Robin Thicke got back to performing tonight and wasted no time using the stage to beg for Paula Patton's mercy ... opening up to the crowd about the break-up and dedicating a song to her.
Thicke wore his wedding ring through the show in Fairfax, VA and told the crowd -- "For y'all that don't know me and my wife separated, but I'm trying to get my girl back. She's a good woman."
He also told fans he'd written the song "Lost Without U" for Paula ... before launching into the hit -- which we gotta say is kinda the perfect song for a guy trying to get back on a chick's good side.
Then again, Paula's heard this tune a hundred times.