Trinidad James just got busted for possession of marijuana after lighting up in his Mississippi hotel room ... TMZ has learned.
Cops in Panola County tell us the rapper -- real name Nicholas Williams -- is in custody and being booked right now.
We're told Trini -- whose biggest hit is "All Gold Everything" -- was arrested at the Batesville, MS Holiday Inn.
Just 2 nights ago he was hanging with Diddy, Jermaine Dupri, T.I., and Justin Bieber ... in an Atlanta nightclub.
Looks like Bieber's recent luck rubbed off on Trinidad.