The ballad marks the fourth UK single from Swift's hit album Red, following in the footsteps of her uptempo ode to youthful shenanigans, 22. It is currently unknown whether the pair are planning to shoot a video for the track.
Over the past two months, Sheeran has been supporting Swift on the North-American dates of her world tour, with Taylor yet to reveal whether Ed will be joining her for the UK leg.
Sheeran admitted back in February that there's a good chance they could end up collaborating on new music again, spending their downtime on the road writing tunes with one another.
"We're male and female, but we do exactly the same thing like we're both the same age, we both write songs with guitars we both tour playing acoustic music and that's kind of it," Ed said of their songwriting compatibility.
"We've got a similar sense of humour. I guess we just have a lot in common."
In fact, Sheeran previously admitted that songwriting session with Swift can be pretty spur of the moment. "Taylor writes songs in all different situations," Sheeran told us last summer.
"I remember we went out… I think we were in the car to the studio and she took her phone out and mumbled something and sort of put it back. And I was like 'What was that?' and she was like 'Oh, I was just singing down ideas.'
"She does that all the time. It's a good way to do it. She's one of very few people left in the industry that actually worries about the songs that she sings, like she actually wants to write them herself," he added. "Which I think is a very positive thing."
Sheeran was recently forced to deny rumours romantically linking him to Taylor, stating he 'felt like a bit of a stud' when his friends believed they were an item.