Paul Mescal On Date With Gracie Abrams in London

We have a possible new couple alert from across the pond ... because we just got photos of Paul Mescal on a date with Gracie Abrams .

Check it out ... the Irish star and the "us." singer are sitting at a tiny table together inside a packed restaurant for what appears to be a dinner date.

Folks who were there say Paul and Gracie broke bread at BRAT Restaurant in London, where they ordered a bunch of small sharing plates.

Paul and Gracie are locked in what seems to be a pretty enthralling conversation ... and at one point he even reaches over and strokes her cheek.

The outing comes on the heels of Gracie releasing her second album, "The Secret of Us" ... which features a collab with Taylor Swift -- the one they spent all night writing at Tay Tay's NYC apartment when TS put out a kitchen fire .

Paul's already cozied up to Ayo Edebiri and Natalie Portman this year ... but both instances turned out to be the friendly type.

This looks a little more romantic, though, and it will be interesting to see if there's a spark.