Taylor Swift Joins Beyoncé at Renaissance Premiere in London

Taylor Swift has officially returned the favor to Beyoncé ... showing face at Queen Bey's "Renaissance" movie premiere in London.

The pop star was all glamor, with a glittering strapless gown, wavy hair and red lipstick ... hitting the carpet before Beyoncé arrived.

Of course, when she showed up, Queen Bey had fans in a frenzy ... wearing a sparkling black dress -- she also had 11-year-old daughter Blue Ivy by her side.

Tay and B made the most of their night out in the British capital ... posing for professional red carpet snaps, Taylor also took selfies with die-hard fans.

The "Karma" singer was clearly thrilled to be at the event, proving that even though her relationship with BF Travis Kelce was gaining momentum ... she was willing to ditch him in Kansas City to champion her pal on her big night.

It was only a few weeks ago when Beyoncé showed up to Taylor's "Eras" tour movie premiere in Los Angeles ... so there was a big suspicion Taylor would do the same.