Cee Lo -- Please UN-BAN Me From Chattanooga!!

Cee Lo tells TMZ ... he feels terrible after being banned from a music festival in Chattanooga, TN for dropping too many f-bombs on stage -- and now he's begging for forgiveness.

It's a pretty crazy story ... the organizers of the Riverbend Festival blasted Cee Lo after his June 8 performance, claiming the singer completely ignored an agreement he made to put on a clean show for the "family" event. Instead, they say, Cee Lo cussed like a sailor.

Cee Lo also took heat for being late to the show ... though event organizers said there were delays at the airport that were beyond Cee Lo's control.

Still, when Cee Lo arrived to Playhouse nightclub in Hollywood last night, he had a message for Chattanooga -- "I apologize."

He adds, "Forgive me Chattanooga ... have me back, OK?"