Following a suggestion from his mother, on 11 April 2010, Styles auditioned as a solo contestant for the seventh series of the British televised singing competition The X Factor, singing a rendition of Train's "Hey, Soul Sister". After Simon Cowell suggested that the track was not right for him, he instead sang a rendition of Stevie Wonder's "Isn't She Lovely". He advanced to bootcamp but failed to progress further to the "Boys" category of the competition. Four other solo contestants in his age group who were also eliminated were put together to form a boy band in July 2010 to compete in the "Groups" category, mentored by Cowell.

The group consisting of Styles, Niall Horan, Liam Payne, Louis Tomlinson, and Zayn Malik practised for two weeks; Styles suggested the name One Direction to his colleagues which they agreed to. They began to gain considerable popularity in the UK, and within the first four weeks of the live shows, were Cowell's last contestant in the competition. The group eventually reached the final of The X Factor and became the last contestant eliminated on the show.

In January 2011, One Direction signed a recording contract with Cowell's label Syco Records. Their UK number one debut single, "What Makes You Beautiful", and their debut studio album, Up All Night, were released later that year. The album, which contained three songs co-written by Styles, debuted at number one in the United States. Their four succeeding studio albums—Take Me Home (2012), Midnight Memories (2013), Four (2014) and Made in the A.M. (2015)—all debuted at number one in the UK.

Midnight Memories was the world's best-selling album of 2013, and its accompanying Where We Are Tour was the highest-grossing tour of 2014. After the release of Four, One Direction became the only group in the 58-year history of the Billboard 200 albums chart to have their first four albums debut at number one. The albums spawned a string of successful singles, including "Live While We're Young", "Little Things", "Best Song Ever", "Story of My Life", "Drag Me Down" and "History". Styles also co-wrote the song "Just a Little Bit of Your Heart" for Ariana Grande's 2014 album My Everything.

Not wanting to "exhaust" the fan base, upon Styles's suggestion, One Direction went on an indefinite hiatus in 2016, after completing promotional activities related to Made in the A.M. As of March 2015, One Direction have sold 70 million records worldwide since their debut, including 7.6 million albums and 26 million singles in the US, becoming one of the best-selling boy bands of all time. The group amassed numerous accolades, including seven Brit Awards, seven American Music Awards, six Billboard Music Awards, and four MTV Video Music Awards.

While Styles has been generally positive about his time in One Direction, he has revealed that the hyper-visibility he experienced while being in the band was not always easy to deal with. Styles attributed his avoidance of social media to past pressure that he should be constantly accessible online. He has spoken about being scared of saying the wrong things in interviews and of fear that not answering questions such as the number of people he slept with would cause journalists to leave the interview annoyed with him. His contracts with One Direction contained "cleanliness clauses" which stated that the group would be "null and void" if he did not obey them. He expressed that he "burst into tears" when he signed a solo contract without these clauses because he felt "free."

As a solo artist, Styles joined Jeffrey Azoff's Full Stop Management and talent agency CAA, signing a recording contract with Columbia Records in the first half of 2016. Around this time, he also launched his own record label, Erskine Records. Recording for Styles's debut album occurred throughout 2016 in Los Angeles, London and Port Antonio, Jamaica, where Styles and his collaborators spent a two-month writing retreat in the autumn. In March 2017, he announced that his first solo single, "Sign of the Times", would be released on 7 April. The song peaked at number one on the UK Singles Chart and number four on the US Billboard Hot 100. A glam rock-influenced soft rock power ballad, it drew comparisons to the work of David Bowie. Rolling Stone ranked "Sign of the Times" as the best song of 2017. Its music video featured Styles flying and walking on water and won the Brit Award for British Video of the Year. In April, Styles was a musical guest on Saturday Night Live in the US and made his debut televised solo performance in the UK on The Graham Norton Show.

Styles's debut studio album, Harry Styles, was released in May 2017, whereupon it debuted at number one in several countries, including Australia, the UK and the US. The record was influenced by 1970s soft rock and was described by Variety as a "classic cocktail of psychedelia, Britpop, and balladry." It received generally favourable reviews from critics and was included in several publications' lists of the best albums of 2017. Harry Styles yielded two more singles, "Two Ghosts" and "Kiwi". The film Harry Styles: Behind the Album, which documented the writing and recording process for the album, was released in May exclusively on Apple Music. Styles embarked on his first headlining concert tour, Harry Styles: Live on Tour, from September 2017 through to July 2018, performing in North and South Americas, Europe, Asia, and Australia. During the tour, Styles debuted two unreleased songs, "Anna" and "Medicine".

Styles made his feature film debut in Christopher Nolan's war film Dunkirk, in July 2017, playing a British soldier named Alex in the Dunkirk evacuation during World War II. He appeared alongside an ensemble cast which included Fionn Whitehead, Tom Glynn-Carney, Jack Lowden, Kenneth Branagh, Cillian Murphy, Mark Rylance, and Tom Hardy. Styles won the part over "thousands of young men"; Nolan later admitted he was unaware of the extent of Styles's fame and that he was cast "because he fit the part wonderfully and truly earned a seat at the table." The Daily Telegraph film critic Robbie Collin praised Styles for his "bright, convicted, and unexpectedly not-at-all-jarring performance."

In November 2017, BBC One broadcast Harry Styles at the BBC, a one-hour television special presented by Nick Grimshaw. Later that month, he performed at the Victoria's Secret Fashion Show held in Shanghai. At the 2017 ARIA Music Awards, Styles received the Best International Artist award. He guest-hosted The Late Late Show with James Corden in December. Together with Jack Antonoff and Ilsey Juber, Styles co-wrote "Alfie's Song (Not So Typical Love Song)", performed by the band Bleachers, for the soundtrack of the film Love, Simon (2018). He also served as an executive producer on CBS's sitcom Happy Together, which premiered in October 2018 and was inspired by his time living with television producer Ben Winston and his wife. In 2018, Styles began modelling for the Italian fashion house Gucci, appearing in several campaigns for the brand.

In July 2019, it was reported that Styles was in early talks to play Prince Eric in the live-action Disney film The Little Mermaid (2023). He ultimately turned the part down for various reasons which included touring and wanting to pursue darker roles. "Lights Up", the lead single from Styles's second album, Fine Line, was released in October 2019, debuting at number three in the UK. The song featured a "soft-touch re-entry into the pop slipstream", according to music writer Jon Caramanica. Styles served as both host and musical guest on Saturday Night Live in November. The second single preceding Fine Line, "Adore You", was released in December, peaking at number seven in the UK and number six in the US. That month, Styles again guest-hosted The Late Late Show with James Corden.

Fine Line was released on 13 December. The album was recorded at the Shangri-La studio in Malibu, California, with the same production team behind Styles's debut album, and features a similar sound to Harry Styles while also incorporating elements of funk and soul. It received generally positive reviews from critics. The album peaked at number two in the UK and topped the US charts, breaking the record as the biggest sales debut from an English male artist in the US since Nielsen SoundScan began electronically tracking sales data in 1991. Rolling Stone ranked it at number 491 in their 2020 list of the "500 Greatest Albums of All Time". Five other singles, "Falling", "Watermelon Sugar", "Golden", "Treat People with Kindness", and the title track, were released from the album. "Watermelon Sugar" became Styles's fourth UK top-ten single, peaking at number four, as well as his first number-one single in the US. A tour to support Fine Line, entitled Love On Tour, which was originally set to take place throughout 2020, was postponed until 2021 due to the COVID-19 pandemic.

At the 2020 Brit Awards, Styles was nominated for British Male Solo Artist and British Album of the Year. In March 2020, he performed an NPR Tiny Desk concert, and in July, he narrated a bedtime story titled Dream with Me for the relaxation app Calm. Styles co-wrote the song "Changes" for Cam's album The Otherside. Later that year, Styles won the Favorite Pop/Rock Album award for Fine Line at the 48th American Music Awards, the Best International Artist award at the 34th ARIA Music Awards, and the Chart Achievement Award at the 27th Billboard Music Awards. He was also named Variety's Hitmaker of the Year. At the 63rd Annual Grammy Awards in March 2021, he received three nominations for Best Pop Vocal Album (Fine Line), Best Pop Solo Performance ("Watermelon Sugar"), and Best Music Video ("Adore You"), winning for Best Pop Solo Performance. "Watermelon Sugar" also earned Styles his second Brit Award for British Single of the Year during the 2021 ceremony. After previous postponement, Love On Tour kicked off on 4 September 2021 in Las Vegas. At the 2021 Ivor Novello Awards, "Adore You" won the award for Most Performed Work. Styles made a cameo appearance as Eros / Starfox, brother of Thanos, in the mid-credits scene of the Marvel Cinematic Universe superhero film Eternals, released in November 2021. He launched his gender-neutral skin and nail care brand, Pleasing, that month.

In 2022, Styles achieved critical and commercial success with his third album, Harry's House. Its lead single, "As It Was", debuted atop the UK and US charts, becoming his second solo number-one single in both countries. In the US, it became the fourth-longest-running number-one in history, at 15 weeks. The album similarly debuted atop the UK and US charts. During Harry's House's release week, Styles occupied the top spot of the album and singles charts in over fifteen countries, with Harry's House and "As It Was". He became the first British solo artist to have four tracks concurrently charting within the US top 10.

Styles headlined the Coachella Valley Music and Arts Festival in April to a crowd of over 100,000 people. In June 2022, Styles and the single "Music for a Sushi Restaurant" were featured in an AirPods commercial. The following month, Harry's House was short-listed for the Mercury Prize. "As It Was" became Billboard's number-one song of 2022 globally and IFPI's best-selling global single of the year. At the 2022 MTV Video Music Awards, Styles received three accolades, including Album of the Year for Harry's House. The album also won Album of the Year and Best Pop Vocal Album at the 65th Grammy Awards, and British Album of the Year at the 43rd Brit Awards. At the 50th American Music Awards, Styles won Favorite Male Pop Artist and Favorite Pop Song ("As It Was"). Rolling Stone ranked Harry's House at number 491 on its 2023 revision of the "500 Greatest Albums of All Time" list.

Styles auditioned for the role of Elvis Presley in Baz Luhrmann's musical biopic Elvis (2022). Luhrmann stated that while "Harry is a really talented actor ... the real issue with Harry is, he's Harry Styles. He's already an icon." Styles starred alongside Florence Pugh in the 2022 psychological thriller film Don't Worry Darling, directed by Olivia Wilde. Having premiered at the 79th Venice International Film Festival, the film, as well as his performance, received mixed reviews. Steph Green from the BBC wrote, "Harry Styles doesn't feel up to the material here, with leaden line delivery and a lack of light and shade making his scenes opposite Pugh fall flat". Some critics were more positive; Owen Gleiberman from Variety wrote, "With his popping eyes, floppy shock of hair, and saturnine suaveness, he recalls the young Frank Sinatra as an actor". Styles also starred alongside David Dawson and Emma Corrin in the romantic drama film My Policeman, which premiered at the 2022 Toronto International Film Festival. The film's main cast members were awarded the TIFF Tribute Award for Performance. Critics were divided on the film and Styles's performance. Robert Daniels of RogerEbert.com wrote, "Here, Styles' inexperience as a leading man in a weepy British queer period piece is glaring", while Caryn James from the BBC opined that Styles "is far more convincing and has a much fuller, more grounded role in My Policeman" compared to his Don't Worry Darling performance.

In August and September 2022, as part of his Love On Tour, Styles performed 15 sold-out shows at Madison Square Garden; to mark the achievement, a permanent banner was raised inside the venue. Styles became the third musical artist in history to have a banner raised at Madison Square Garden. In November 2022, Styles collaborated with Alessandro Michele on a Gucci collection titled "Gucci Ha Ha Ha". Love On Tour concluded in July 2023 as the then-fifth-highest-grossing tour of all time, earning $617.3 million. Styles provided background vocals on bandmate Mitch Rowland's track "Here Comes the Comeback", released in September 2023. In July 2024, Styles joined Stevie Nicks on stage at the British Summer Time festival in London to perform "Stop Draggin' My Heart Around" and "Landslide" in tribute of Christine McVie's birthday.

In late December 2025, Styles shared a video to his YouTube channel entitled "Forever, Forever". The eight-and-a-half minute video depicted the final night of Love On Tour at RCF Arena Campovolo in Reggio Emilia circa July 2023. It also showed footage of the final song performed that evening, which was an untitled ambient instrumental composition that featured Styles on piano. The video ended with the words "we belong together" appearing on the screen.

On 12 January 2026, posters displaying that same phrase were discovered in various cities globally. These posters directed individuals to a website, which subsequently redirected them to a WhatsApp group. Two days later, a voice memo of Styles mumbling "we belong together" was sent to fans through text. On 15 January 2026, Styles announced his fourth studio album, entitled Kiss All the Time. Disco, Occasionally. The album was released on 6 March 2026. The lead single, "Aperture", was announced on 20 January and released on 23 January. On 22 January, Styles announced Together, Together, a series of concert residencies in seven cities.

In 2026, Harry Styles was announced as the curator of the 31st edition of Meltdown Festival, to be held at the Southbank Centre in London. The 2026 edition forms part of the Centre’s 75th anniversary year, with Styles headlining the festival and curating the programme of musical and cultural events.

Music critics have described Styles as having a baritone singing voice. They described his music as pop, pop rock, rock, soft rock, Britpop, new wave, synth-pop and disco, with elements of folk. The musical style on his debut solo album was called a "mish-mash of Los Angeles' style classic rock and ballads" by NME, invoking an "intimately emotional Seventies soft-rock vibe" by Rolling Stone, and "synthesis[ing] influences from the last half-century of rock" by Time. It was influenced by the artists he grew up listening to, such as Pink Floyd, the Rolling Stones, the Beatles and Fleetwood Mac, as well as the "honest" songwriting of Harry Nilsson. Fine Line was seen by NME to have taken "this nostalgic sound [from his first record] and combined it with soaring pop sensibilities." Styles said, "I think with music it's so important to evolve—and that extends to clothes and videos and all that stuff. That's why you look back at David Bowie with Ziggy Stardust or the Beatles and their different eras—that fearlessness is super inspiring."

Styles cited Freddie Mercury, Elvis Presley, and Paul McCartney (including his side project Wings) as influences, while mentioning Shania Twain as his main inspiration both musically and in fashion. While making Fine Line, Styles said he kept watching a vintage pep talk by Bowie that inspired him to push his art further. When curating an "all-time top ten tracks" mixtape for Another Man, Styles included tracks by Crosby, Stills & Nash, Ray Charles, Blaze Foley, Patsy Cline, and Travis. Upon listening to Pink Floyd's 1973 album The Dark Side of the Moon as a child, he said he "couldn't really get it, but I just remember being like—this is really fucking cool." The first song Styles learned the words to was "Dreams" (1977) by Fleetwood Mac, although as a child he believed the song "was about the weather."

Styles was also inspired by George Michael, sampling "Faith" (1987) on his unreleased track "Anna", and also has lyrics from "Careless Whisper" (1984) tattooed on his ankles. Joni Mitchell's album Blue (1971) inspired Styles to contact the album's dulcimer instrumentalist, with whom he worked on Fine Line. He also chose to record Fine Line in Henson Recording Studios after being inspired by Carole King's album Tapestry (1971), which was recorded there. During the COVID-19 lockdown, Styles highlighted Mac Miller's 2020 single "Blue World" as his personal quarantine track of choice. He also compiled a playlist for Apple Music during lockdown, inclusive of artists such as Otis Redding, Sam Cooke, Bill Withers, Billie Holiday, Bread, and Labi Siffre. While writing Harry's House in Tokyo, Styles was inspired by Haruomi Hosono's 1973 debut album Hosono House and paid homage to its title. Joni Mitchell, whose 1975 album The Hissing of Summer Lawns featured the track "Harry's House", tweeted that she "love[d] the title." Gerry Rafferty's 1978 single "Right Down the Line" was a specific reference point during the creation of Harry's House.

Styles also cited fine art as an inspiration. He has an extensive private art collection, owning original works from artists such as Jean-Michel Basquiat, Damien Hirst, Polly Morgan, Yunizar, Ben Turnbull, Jessica Zoob, and Hayden Kays. He was also inspired by English painter David Hockney. In 2023, Hockney painted a portrait of Styles included in the David Hockney: Drawing From Life exhibition at the National Portrait Gallery in London. Styles called the experience a "complete privilege" and that "Hockney has been reinventing the way we look at the world for decades." Styles also said that Alain de Botton's 2016 novel The Course of Love made him appreciate the work required in cultivating and sustaining a romantic bond.

Many musicians have expressed getting inspiration from Styles and their desire to work with him. Artists such as SZA, Miley Cyrus, Elton John, Shania Twain, Olivia Rodrigo, Chris Stapleton, Mark Ronson, Halsey, Lorde, Matty Healy, John Legend, and Troye Sivan have all voiced their wishes to collaborate with Styles. However, when asked about collaborating with other artists, Styles joked that he is an "antisocial musician." Singer-songwriter Stevie Nicks likened his album Fine Line to Fleetwood Mac's album Rumours (1977) and commented that she was inspired by him to write new music and poetry.

Novels inspired by Styles include the After series, Grace and the Fever, and The Idea of You. The After novels were turned into a film series, and Anne Hathaway starred in the romantic comedy film The Idea of You (2024), an adaption of the novel. Children's books include Harry Styles: A Little Golden Book Biography and Have You Heard of Harry Styles?.

In June 2024, Styles's childhood village Holmes Chapel launched a 2.5–3 hour guided walking tour around the area. The tour follows the bakery where Styles used to work, the Twemlow Viaduct featured in the One Direction documentary, One Direction: This Is Us (2013), where Styles signs his name, and other attractions. The Holmes Chapel Partnership were forced to hire tour guides to cope with demand after 5,000 fans visited the village in 2023. There were over 150 applications for the role of a tour guide. Madame Tussauds wax museum has displayed a Styles wax figure since his time in One Direction, and as of 2023, Tussaud museums in several countries had a figure of him.

Following a suggestion from his mother, on 11 April 2010, Styles auditioned as a solo contestant for the seventh series of the British televised singing competition The X Factor, singing a rendition of Train's "Hey, Soul Sister". After Simon Cowell suggested that the track was not right for him, he instead sang a rendition of Stevie Wonder's "Isn't She Lovely". He advanced to bootcamp but failed to progress further to the "Boys" category of the competition. Four other solo contestants in his age group who were also eliminated were put together to form a boy band in July 2010 to compete in the "Groups" category, mentored by Cowell.

The group consisting of Styles, Niall Horan, Liam Payne, Louis Tomlinson, and Zayn Malik practised for two weeks; Styles suggested the name One Direction to his colleagues which they agreed to. They began to gain considerable popularity in the UK, and within the first four weeks of the live shows, were Cowell's last contestant in the competition. The group eventually reached the final of The X Factor and became the last contestant eliminated on the show.

In January 2011, One Direction signed a recording contract with Cowell's label Syco Records. Their UK number one debut single, "What Makes You Beautiful", and their debut studio album, Up All Night, were released later that year. The album, which contained three songs co-written by Styles, debuted at number one in the United States. Their four succeeding studio albums—Take Me Home (2012), Midnight Memories (2013), Four (2014) and Made in the A.M. (2015)—all debuted at number one in the UK.

Midnight Memories was the world's best-selling album of 2013, and its accompanying Where We Are Tour was the highest-grossing tour of 2014. After the release of Four, One Direction became the only group in the 58-year history of the Billboard 200 albums chart to have their first four albums debut at number one. The albums spawned a string of successful singles, including "Live While We're Young", "Little Things", "Best Song Ever", "Story of My Life", "Drag Me Down" and "History". Styles also co-wrote the song "Just a Little Bit of Your Heart" for Ariana Grande's 2014 album My Everything.

Not wanting to "exhaust" the fan base, upon Styles's suggestion, One Direction went on an indefinite hiatus in 2016, after completing promotional activities related to Made in the A.M. As of March 2015, One Direction have sold 70 million records worldwide since their debut, including 7.6 million albums and 26 million singles in the US, becoming one of the best-selling boy bands of all time. The group amassed numerous accolades, including seven Brit Awards, seven American Music Awards, six Billboard Music Awards, and four MTV Video Music Awards.

While Styles has been generally positive about his time in One Direction, he has revealed that the hyper-visibility he experienced while being in the band was not always easy to deal with. Styles attributed his avoidance of social media to past pressure that he should be constantly accessible online. He has spoken about being scared of saying the wrong things in interviews and of fear that not answering questions such as the number of people he slept with would cause journalists to leave the interview annoyed with him. His contracts with One Direction contained "cleanliness clauses" which stated that the group would be "null and void" if he did not obey them. He expressed that he "burst into tears" when he signed a solo contract without these clauses because he felt "free."

As a solo artist, Styles joined Jeffrey Azoff's Full Stop Management and talent agency CAA, signing a recording contract with Columbia Records in the first half of 2016. Around this time, he also launched his own record label, Erskine Records. Recording for Styles's debut album occurred throughout 2016 in Los Angeles, London and Port Antonio, Jamaica, where Styles and his collaborators spent a two-month writing retreat in the autumn. In March 2017, he announced that his first solo single, "Sign of the Times", would be released on 7 April. The song peaked at number one on the UK Singles Chart and number four on the US Billboard Hot 100. A glam rock-influenced soft rock power ballad, it drew comparisons to the work of David Bowie. Rolling Stone ranked "Sign of the Times" as the best song of 2017. Its music video featured Styles flying and walking on water and won the Brit Award for British Video of the Year. In April, Styles was a musical guest on Saturday Night Live in the US and made his debut televised solo performance in the UK on The Graham Norton Show.

Styles's debut studio album, Harry Styles, was released in May 2017, whereupon it debuted at number one in several countries, including Australia, the UK and the US. The record was influenced by 1970s soft rock and was described by Variety as a "classic cocktail of psychedelia, Britpop, and balladry." It received generally favourable reviews from critics and was included in several publications' lists of the best albums of 2017. Harry Styles yielded two more singles, "Two Ghosts" and "Kiwi". The film Harry Styles: Behind the Album, which documented the writing and recording process for the album, was released in May exclusively on Apple Music. Styles embarked on his first headlining concert tour, Harry Styles: Live on Tour, from September 2017 through to July 2018, performing in North and South Americas, Europe, Asia, and Australia. During the tour, Styles debuted two unreleased songs, "Anna" and "Medicine".

Styles made his feature film debut in Christopher Nolan's war film Dunkirk, in July 2017, playing a British soldier named Alex in the Dunkirk evacuation during World War II. He appeared alongside an ensemble cast which included Fionn Whitehead, Tom Glynn-Carney, Jack Lowden, Kenneth Branagh, Cillian Murphy, Mark Rylance, and Tom Hardy. Styles won the part over "thousands of young men"; Nolan later admitted he was unaware of the extent of Styles's fame and that he was cast "because he fit the part wonderfully and truly earned a seat at the table." The Daily Telegraph film critic Robbie Collin praised Styles for his "bright, convicted, and unexpectedly not-at-all-jarring performance."

In November 2017, BBC One broadcast Harry Styles at the BBC, a one-hour television special presented by Nick Grimshaw. Later that month, he performed at the Victoria's Secret Fashion Show held in Shanghai. At the 2017 ARIA Music Awards, Styles received the Best International Artist award. He guest-hosted The Late Late Show with James Corden in December. Together with Jack Antonoff and Ilsey Juber, Styles co-wrote "Alfie's Song (Not So Typical Love Song)", performed by the band Bleachers, for the soundtrack of the film Love, Simon (2018). He also served as an executive producer on CBS's sitcom Happy Together, which premiered in October 2018 and was inspired by his time living with television producer Ben Winston and his wife. In 2018, Styles began modelling for the Italian fashion house Gucci, appearing in several campaigns for the brand.

In July 2019, it was reported that Styles was in early talks to play Prince Eric in the live-action Disney film The Little Mermaid (2023). He ultimately turned the part down for various reasons which included touring and wanting to pursue darker roles. "Lights Up", the lead single from Styles's second album, Fine Line, was released in October 2019, debuting at number three in the UK. The song featured a "soft-touch re-entry into the pop slipstream", according to music writer Jon Caramanica. Styles served as both host and musical guest on Saturday Night Live in November. The second single preceding Fine Line, "Adore You", was released in December, peaking at number seven in the UK and number six in the US. That month, Styles again guest-hosted The Late Late Show with James Corden.

Fine Line was released on 13 December. The album was recorded at the Shangri-La studio in Malibu, California, with the same production team behind Styles's debut album, and features a similar sound to Harry Styles while also incorporating elements of funk and soul. It received generally positive reviews from critics. The album peaked at number two in the UK and topped the US charts, breaking the record as the biggest sales debut from an English male artist in the US since Nielsen SoundScan began electronically tracking sales data in 1991. Rolling Stone ranked it at number 491 in their 2020 list of the "500 Greatest Albums of All Time". Five other singles, "Falling", "Watermelon Sugar", "Golden", "Treat People with Kindness", and the title track, were released from the album. "Watermelon Sugar" became Styles's fourth UK top-ten single, peaking at number four, as well as his first number-one single in the US. A tour to support Fine Line, entitled Love On Tour, which was originally set to take place throughout 2020, was postponed until 2021 due to the COVID-19 pandemic.

At the 2020 Brit Awards, Styles was nominated for British Male Solo Artist and British Album of the Year. In March 2020, he performed an NPR Tiny Desk concert, and in July, he narrated a bedtime story titled Dream with Me for the relaxation app Calm. Styles co-wrote the song "Changes" for Cam's album The Otherside. Later that year, Styles won the Favorite Pop/Rock Album award for Fine Line at the 48th American Music Awards, the Best International Artist award at the 34th ARIA Music Awards, and the Chart Achievement Award at the 27th Billboard Music Awards. He was also named Variety's Hitmaker of the Year. At the 63rd Annual Grammy Awards in March 2021, he received three nominations for Best Pop Vocal Album (Fine Line), Best Pop Solo Performance ("Watermelon Sugar"), and Best Music Video ("Adore You"), winning for Best Pop Solo Performance. "Watermelon Sugar" also earned Styles his second Brit Award for British Single of the Year during the 2021 ceremony. After previous postponement, Love On Tour kicked off on 4 September 2021 in Las Vegas. At the 2021 Ivor Novello Awards, "Adore You" won the award for Most Performed Work. Styles made a cameo appearance as Eros / Starfox, brother of Thanos, in the mid-credits scene of the Marvel Cinematic Universe superhero film Eternals, released in November 2021. He launched his gender-neutral skin and nail care brand, Pleasing, that month.

In 2022, Styles achieved critical and commercial success with his third album, Harry's House. Its lead single, "As It Was", debuted atop the UK and US charts, becoming his second solo number-one single in both countries. In the US, it became the fourth-longest-running number-one in history, at 15 weeks. The album similarly debuted atop the UK and US charts. During Harry's House's release week, Styles occupied the top spot of the album and singles charts in over fifteen countries, with Harry's House and "As It Was". He became the first British solo artist to have four tracks concurrently charting within the US top 10.

Styles headlined the Coachella Valley Music and Arts Festival in April to a crowd of over 100,000 people. In June 2022, Styles and the single "Music for a Sushi Restaurant" were featured in an AirPods commercial. The following month, Harry's House was short-listed for the Mercury Prize. "As It Was" became Billboard's number-one song of 2022 globally and IFPI's best-selling global single of the year. At the 2022 MTV Video Music Awards, Styles received three accolades, including Album of the Year for Harry's House. The album also won Album of the Year and Best Pop Vocal Album at the 65th Grammy Awards, and British Album of the Year at the 43rd Brit Awards. At the 50th American Music Awards, Styles won Favorite Male Pop Artist and Favorite Pop Song ("As It Was"). Rolling Stone ranked Harry's House at number 491 on its 2023 revision of the "500 Greatest Albums of All Time" list.

Styles auditioned for the role of Elvis Presley in Baz Luhrmann's musical biopic Elvis (2022). Luhrmann stated that while "Harry is a really talented actor ... the real issue with Harry is, he's Harry Styles. He's already an icon." Styles starred alongside Florence Pugh in the 2022 psychological thriller film Don't Worry Darling, directed by Olivia Wilde. Having premiered at the 79th Venice International Film Festival, the film, as well as his performance, received mixed reviews. Steph Green from the BBC wrote, "Harry Styles doesn't feel up to the material here, with leaden line delivery and a lack of light and shade making his scenes opposite Pugh fall flat". Some critics were more positive; Owen Gleiberman from Variety wrote, "With his popping eyes, floppy shock of hair, and saturnine suaveness, he recalls the young Frank Sinatra as an actor". Styles also starred alongside David Dawson and Emma Corrin in the romantic drama film My Policeman, which premiered at the 2022 Toronto International Film Festival. The film's main cast members were awarded the TIFF Tribute Award for Performance. Critics were divided on the film and Styles's performance. Robert Daniels of RogerEbert.com wrote, "Here, Styles' inexperience as a leading man in a weepy British queer period piece is glaring", while Caryn James from the BBC opined that Styles "is far more convincing and has a much fuller, more grounded role in My Policeman" compared to his Don't Worry Darling performance.

In August and September 2022, as part of his Love On Tour, Styles performed 15 sold-out shows at Madison Square Garden; to mark the achievement, a permanent banner was raised inside the venue. Styles became the third musical artist in history to have a banner raised at Madison Square Garden. In November 2022, Styles collaborated with Alessandro Michele on a Gucci collection titled "Gucci Ha Ha Ha". Love On Tour concluded in July 2023 as the then-fifth-highest-grossing tour of all time, earning $617.3 million. Styles provided background vocals on bandmate Mitch Rowland's track "Here Comes the Comeback", released in September 2023. In July 2024, Styles joined Stevie Nicks on stage at the British Summer Time festival in London to perform "Stop Draggin' My Heart Around" and "Landslide" in tribute of Christine McVie's birthday.

In late December 2025, Styles shared a video to his YouTube channel entitled "Forever, Forever". The eight-and-a-half minute video depicted the final night of Love On Tour at RCF Arena Campovolo in Reggio Emilia circa July 2023. It also showed footage of the final song performed that evening, which was an untitled ambient instrumental composition that featured Styles on piano. The video ended with the words "we belong together" appearing on the screen.

On 12 January 2026, posters displaying that same phrase were discovered in various cities globally. These posters directed individuals to a website, which subsequently redirected them to a WhatsApp group. Two days later, a voice memo of Styles mumbling "we belong together" was sent to fans through text. On 15 January 2026, Styles announced his fourth studio album, entitled Kiss All the Time. Disco, Occasionally. The album was released on 6 March 2026. The lead single, "Aperture", was announced on 20 January and released on 23 January. On 22 January, Styles announced Together, Together, a series of concert residencies in seven cities.

In 2026, Harry Styles was announced as the curator of the 31st edition of Meltdown Festival, to be held at the Southbank Centre in London. The 2026 edition forms part of the Centre’s 75th anniversary year, with Styles headlining the festival and curating the programme of musical and cultural events.

Music critics have described Styles as having a baritone singing voice. They described his music as pop, pop rock, rock, soft rock, Britpop, new wave, synth-pop and disco, with elements of folk. The musical style on his debut solo album was called a "mish-mash of Los Angeles' style classic rock and ballads" by NME, invoking an "intimately emotional Seventies soft-rock vibe" by Rolling Stone, and "synthesis[ing] influences from the last half-century of rock" by Time. It was influenced by the artists he grew up listening to, such as Pink Floyd, the Rolling Stones, the Beatles and Fleetwood Mac, as well as the "honest" songwriting of Harry Nilsson. Fine Line was seen by NME to have taken "this nostalgic sound [from his first record] and combined it with soaring pop sensibilities." Styles said, "I think with music it's so important to evolve—and that extends to clothes and videos and all that stuff. That's why you look back at David Bowie with Ziggy Stardust or the Beatles and their different eras—that fearlessness is super inspiring."

Styles cited Freddie Mercury, Elvis Presley, and Paul McCartney (including his side project Wings) as influences, while mentioning Shania Twain as his main inspiration both musically and in fashion. While making Fine Line, Styles said he kept watching a vintage pep talk by Bowie that inspired him to push his art further. When curating an "all-time top ten tracks" mixtape for Another Man, Styles included tracks by Crosby, Stills & Nash, Ray Charles, Blaze Foley, Patsy Cline, and Travis. Upon listening to Pink Floyd's 1973 album The Dark Side of the Moon as a child, he said he "couldn't really get it, but I just remember being like—this is really fucking cool." The first song Styles learned the words to was "Dreams" (1977) by Fleetwood Mac, although as a child he believed the song "was about the weather."

Styles was also inspired by George Michael, sampling "Faith" (1987) on his unreleased track "Anna", and also has lyrics from "Careless Whisper" (1984) tattooed on his ankles. Joni Mitchell's album Blue (1971) inspired Styles to contact the album's dulcimer instrumentalist, with whom he worked on Fine Line. He also chose to record Fine Line in Henson Recording Studios after being inspired by Carole King's album Tapestry (1971), which was recorded there. During the COVID-19 lockdown, Styles highlighted Mac Miller's 2020 single "Blue World" as his personal quarantine track of choice. He also compiled a playlist for Apple Music during lockdown, inclusive of artists such as Otis Redding, Sam Cooke, Bill Withers, Billie Holiday, Bread, and Labi Siffre. While writing Harry's House in Tokyo, Styles was inspired by Haruomi Hosono's 1973 debut album Hosono House and paid homage to its title. Joni Mitchell, whose 1975 album The Hissing of Summer Lawns featured the track "Harry's House", tweeted that she "love[d] the title." Gerry Rafferty's 1978 single "Right Down the Line" was a specific reference point during the creation of Harry's House.

Styles also cited fine art as an inspiration. He has an extensive private art collection, owning original works from artists such as Jean-Michel Basquiat, Damien Hirst, Polly Morgan, Yunizar, Ben Turnbull, Jessica Zoob, and Hayden Kays. He was also inspired by English painter David Hockney. In 2023, Hockney painted a portrait of Styles included in the David Hockney: Drawing From Life exhibition at the National Portrait Gallery in London. Styles called the experience a "complete privilege" and that "Hockney has been reinventing the way we look at the world for decades." Styles also said that Alain de Botton's 2016 novel The Course of Love made him appreciate the work required in cultivating and sustaining a romantic bond.

Many musicians have expressed getting inspiration from Styles and their desire to work with him. Artists such as SZA, Miley Cyrus, Elton John, Shania Twain, Olivia Rodrigo, Chris Stapleton, Mark Ronson, Halsey, Lorde, Matty Healy, John Legend, and Troye Sivan have all voiced their wishes to collaborate with Styles. However, when asked about collaborating with other artists, Styles joked that he is an "antisocial musician." Singer-songwriter Stevie Nicks likened his album Fine Line to Fleetwood Mac's album Rumours (1977) and commented that she was inspired by him to write new music and poetry.

Novels inspired by Styles include the After series, Grace and the Fever, and The Idea of You. The After novels were turned into a film series, and Anne Hathaway starred in the romantic comedy film The Idea of You (2024), an adaption of the novel. Children's books include Harry Styles: A Little Golden Book Biography and Have You Heard of Harry Styles?.

In June 2024, Styles's childhood village Holmes Chapel launched a 2.5–3 hour guided walking tour around the area. The tour follows the bakery where Styles used to work, the Twemlow Viaduct featured in the One Direction documentary, One Direction: This Is Us (2013), where Styles signs his name, and other attractions. The Holmes Chapel Partnership were forced to hire tour guides to cope with demand after 5,000 fans visited the village in 2023. There were over 150 applications for the role of a tour guide. Madame Tussauds wax museum has displayed a Styles wax figure since his time in One Direction, and as of 2023, Tussaud museums in several countries had a figure of him.