While the superstar pair haven't confirmed the claims, multiple outlets are reporting they've mutually ended their 15-month relationship.
A source told People: "There was no drama. Things just don't work out sometimes."
An insider added to E! News: "Taylor and [Calvin] had no big blowout fight, but the romance just was not there anymore for them."
If true, it comes as a huge shock, given how loved up and happy they'd appeared recently. It was just in April that Taylor publicly thanked Calvin – real name Adam Wiles - at the iHeartRadio Music Awards.
Accepting a prize, she told the audience: "For the first time, I had the most amazing person to come home to when the spotlight went out and when the crowds were all gone. I want to thank my boyfriend Adam for that."
Taylor, 26, and Calvin, 32, had been relatively open about their relationship, with photos posted to social media, including one celebrating their one-year anniversary in March.
They were introduced by mutual friend Ellie Goulding, who previously told The Sun: "I did play matchmaker, that's true. Calvin is a really great mate and he's so fantastic and Taylor is such a cool person who I love. I thought, 'They're both really awesome and both really tall, they'll be brilliant together!'"
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