Justin Bieber Performs in Undies At Grammy Awards

Justin Bieber knocked the rust off Sunday, returning to the Grammys stage after a 4-year hiatus ... in his underwear!

Watch the clip ... his wife Hailey Bieber nodded along as the singer belted out his song "Yukon" and then just kind of wandered off stage.

The singer has mostly shied away from performing since getting diagnosed with Type 2 Ramsay Hunt Syndrome, which temporarily paralyzed part of his face. The diagnosis caused him to cut his Justice World Tour short in 2022.

JB's album, "Swag," is up for 4 awards tonight, including Album of the Year, Best Pop Solo Performance, Best Pop Vocal Album, and Best R&B Performance.