"Yes I can confirm they have split up," a MailOnline source said.
"They were on holiday and had an almighty row. They are two young stars at the top of their game so who knows what will happen in the future."
Another source told Life & Style magazine that the pair's work commitments got in the way of their love life.
"They are both really busy and never in one place for long," the source said.
"Harry's really upset about the split and is really sensitive about it. Loads of his friends told him to be careful and that it was never going to last, and he feels a little foolish now that it's fallen apart so quickly."
More evidence of their split has come to light, with two men spotting Taylor looking "visibly heartbroken" at the St Thomas airport in the US Virgin Islands on January 4. The men, Mike Zavagno and Jake Hurley, told the New York Post what they saw.
"She looked really sad and lonely, really down," Zavagno said.
Hurley continued: "We had heard she was down there with Harry Styles from One Direction, but the impression that I got was that they must have had a fight or something because she was just with her bodyguard and I said to Mike, 'She looks really sad'".
Taylor wasn't seen crying, but Hurley said that "you could tell that something was visibly wrong".
"She was just sitting there with her hands in her lap, no phone or anything," he said, adding that when people called her name, she waved back but "didn't really get into it".
Meanwhile, in Harry land, the 18-year-old was seen partying for two days at Richard Branson's Necker Island (see hot tub pic above).
When he flew out on Sunday, Harry was spotted "mingling with pretty female fans" over a three-and-a-half hour layover in Puerto Rico.
One witness told the New York Post that Harry seemed "really happy" with his fans, giving hugs, posing for photos, and eventually going out to lunch with them at a nearby Italian restaurant.
Harry headed straight to the recording studio upon his return to London, talking to girls in the street on his way there. Could there be a break-up song in the works?