Performing Gaga's new hit "Do What U Want," which she sings with R.Kelly on the album, the pair of pop stars delivered an absolutely incredible performance.
Gaga started the song off solo and then the Voice judge suddenly emerged from inside a giant sphere at the back of the stage.
Each singer has a powerful set of pipes, but they didn't try to outshine one another and the result was amazing.
"She is such a powerhouse vocalist and I was honored to join the stage with @ladygaga tonight on #TheVoice! xo," Christina tweeted.
Check out the video above and tell us what you think of their performance.