Styles dated Taylor from November 2012 to January 2013. After Taylor ended her relationship with Connor Kennedy in October 2012, she was photographed the following month wearing a paper plane necklace, similar to the one Harry wore at the time. The pair were then photographed holding hands together numerous times, both in New York where Taylor lives, and in Cheshire, Harry's hometown, throughout December 2012. They shared a New Year's Eve kiss in New York City's Times Square. They split five days later, while on vacation, for unknown reasons. Neither have revealed the reason behind their split, though Swift has since described the relationship as "fragile" and full of "anxiety and roadblocks".
Swift's fifth album 1989 features two songs confirmed to be about Harry: "Style" and "Out Of The Woods". Style was released as the third official single from 1989, and became one of the best selling songs of 2015, while Out Of The Woods was released as the sixth official single and peaked at #18. The former references Harry's surname, and Swift holds a paper airplane necklace in the music video. Swift confirmed Out Of The Woods references a December 2012 snow mobile accident she and Harry were in where her "life flashed before [my] eyes". Harry was photographed with bandages on his chin in the immediate aftermath. The referential lyrics are "Remember when you hit the breaks too soon, 20 stitches in the hospital room, when you started crying, baby, I did too". Certain lyrics also reference December and paper airplanes. In October 2015, One Direction released "Perfect", a song co-written by Harry and Louis, featuring the lyric "If you're looking for someone to write your break-up songs about, baby, I'm perfect", which sparked worldwide media speculation of it being a reference to Swift, who is known to write songs detailing her failed relationships.
On 18 April 2017, in a Rolling Stone interview, Harry addressed his relationship with Swift for the first time since their split. When asked to comment, Styles stated: "I don't know if [Style and Out Of The Woods] are about me or not, but the issue is, she's so good, they're bloody everywhere. I write from my experiences; everyone does that. I'm lucky if everything [we went through] helped create those songs. That's what hits your heart. That's the stuff that's hardest to say, and it's the stuff I talk least about. She doesn't need me to tell her the [songs] are great. It's the most amazing unspoken dialogue ever. Certain things don't work out. There's a lot of things that can be right, and it's still wrong. In writing songs about stuff like that, I like tipping a hat to the time together. You're celebrating the fact it was powerful and made you feel something, rather than 'this didn't work out, and that's bad.' And if you run into that person, maybe it's awkward, maybe you have to get drunk ... but you shared something. Meeting someone new, sharing those experiences, it's the best shit ever".
- They were seen taking a stroll in a New York's Central Park December 2, 2012.
- They were photographed singing at One Direction's karaoke afterparty together, following the band's monumental Madison Square Garden concerts. 
- They were seen dancing and sharing a kiss backstage at the Kiss-Z100 Jingle Ball in 2012.
- They attended a mutual friend's birthday party in December 2012.
- Taylor was with Harry when he got his ship tattoo. 
- Harry and Taylor kissed at the stroke of midnight on January 1, 2013 in Times Square. 
- Styles and Swift separately took a photo with mutual friend Ed Sheeran at the 2013 MTV Video Music Awards.
- The two separately attended Kings of Leon singer Nathan Followill's birthday party in January 2015.
- The two were in attendance at the 2015 Billboard Awards and Harry's bandmates Louis Tomlinson and Niall Horan attended Taylor's afterparty.