T-Pain gave fans an emotional surprise at Electric Forest … debuting an unreleased collaboration with the late Oliver Tree while a montage honoring the late artist played across the massive stage screens.

Video from the performance shows T-Pain introducing the never-before-heard track as photos and clips of Oliver filled the screens, creating a touching tribute that left the crowd cheering for the late great star.

Sources with direct knowledge tell TMZ the song is an unreleased collaboration T-Pain and Oliver recorded together in the studio before Oliver’s sudden death.

The tribute happened during T-Pain’s back-to-back set with DJ Diesel — aka Shaquille O’Neal — with the unreleased song serving as one of the night’s biggest surprises.

Fans quickly shared videos across social media, praising T-Pain for honoring his late friend by finally letting people hear the collaboration while celebrating Oliver’s life through the on-screen montage.

As we previously reported … Oliver and five others — including YouTuber Gaspi — died in Brazil after two helicopters collided near Rio de Janeiro.

The late singer’s team wasted no time fulfilling his wishes following his sudden death earlier this month — they’ve officially launched Dr. Oliver Tree’s Extremely Epic Art Grant for Baby Geniuses foundation.

The foundation’s website says it awards money to successful applicants so they can produce and create in music, film, installation, and performance art … and that the projects “should reflect the spirit of the work Oliver Tree created in collaboration with the foundation’s board members during his lifetime.”