Taylor Swift had a special guest performer at her soldout Staples Center show in Los Angeles -- Ellie Goulding!

The 'Red' singer teased the audience about their special guest's identity for a while before finally showing off the U.K. crooner.

"You know, Los Angeles, we've had some really good times together," Swift smiled. "So many fun surprises. And that's not really a tradition I'm ready to stop anytime soon. So I'm just wondering, Los Angeles, how you would feel if there was a special surprise guest performer here tonight?"

The crowd, predictably, went wild.

"Oh good," Swift said, her speech somewhat stilted and sounding slightly scripted, but still adorable. "I was hoping you would say that, because it would be so awkward if you were not excited about the fact that we have an incredible, wonderful, insanely talented, incredibly cool artist about to come onstage and sing for you. She's not from around here, she's actually from the U.K. She's one of my favorite artists. She's also one of my friends."

Then the big reveal: "Hey Los Angeles! Ellie Goulding is here!"

Goulding emerged, wearing a white top and similar black high-waisted shorts as Swift. The duo hugged and danced together, Swift slightly more awkwardly and stiffly. Goulding took the first verse and appeared to have some slight mic issues early in the song, but they resolved quickly. Swift sang the second, and the gals harmonized for the choruses.

Swift and Goulding each tweeted and posted photos of the event, which they were both super excited about:

Anyone else love this mutual girl crush that they have going on?!