Steve-O is firing back at Bam Margera after his former 'Jackass' costar said he sucks at skateboarding ... and he's got video with Tony Hawk backing him up.
In a video response to Bam's diss track, Steve-O brushes off Bam's criticism as jealousy and envy, and then hammers his point home with a skateboard mixtape showing off his skills.
TMZ broke the story ... Bam's featured on a new rap song, and in his verse, he takes shots at all of his former 'Jackass' buddies, mostly knocking Steve-O for his skating ability compared to himself and other pro skaters.
Steve-O says the fans buying his autographed skateboard decks are probably making Bam upset... and he's taking serious offense to Bam's claim he can't skate worth a damn.
Ya gotta see Steve-O's compilation vid -- he's doing kickflips, board slides and wall rides and it's Tony Hawk approved!!!
Remember ... Bam's been beefing with Steve-O ever since they had a falling out on Steve-O's comedy tour, but Steve-O manages to show Bam some love here, despite the diss.