JB hit the stage with WizKid Sunday night at the California music festival, performing their hit song, "Essence" for the excited crowd. Check it out ... the audience goes totally nuts as Justin appears onstage in a black sweatshirt, cargo pants and a baseball hat.

Justin's cameo was a welcome surprise ... as the singer has been keeping a low profile following his Ramsay Hunt Syndrome diagnosis.

Remember, Justin was diagnosed with the rare neurological disorder in June 2022, leading to the cancelation of his "Justice" tour.

Still, Justin has stepped out a bit more in recent months ... with the singer even performing a surprise 6-song set at the NHL All-Star Weekend in Toronto back in February.

Many thought Justin's appearance at the hockey event meant he'd join Usher for the Super Bowl Halftime show, but he ultimately turned down the invitation.

As Lil Jon previously told TMZ ... the SB Halftime show was just too much for Justin to commit to doing. Justin did cheer on Usher from the stands, however, attending the Super Bowl with his wife, Hailey Bieber.

Nonetheless, Justin has a long history of making surprise cameos at Coachella. Not only did Justin stop by Daniel Caesar's Coachella set in 2022 to perform "Peaches," but he also joined Ariana Grande in 2019 for her Coachella set.

Justin had also been spotted enjoying the festival earlier in the weekend, hugging it out Saturday with his longtime pal Jaden Smith.

Justin wasn't the only A-list surprise during Coachella weekend one ... as Will Smith joined J Balvin onstage, Olivia Rodrigo stopped by Gwen Stefani's set, Billie Eilish hit the stage with Lana Del Rey and Kesha was invited by Reneé Rapp to perform a song.