MMA Star Phoenix Jones -- I Stopped An Attempted Murder (VIDEO)

MMA star Phoenix Jones had a busy weekend -- winning his bout on Friday night ... and then BREAKING UP AN ATTEMPTED MURDER roughly 24 hours later.

Jones -- real name Ben Fodor -- was out in Seattle early Sunday morning when he claims he witnessed 3 men attacking another guy outside of a bar ... one of the attackers allegedly had a gun.

So Jones -- who moonlights as a real-life superhero -- says he jumped into action ... KOing the lead attacker who was allegedly pistol-whipping the victim while the other 2 men had been stomping his head.

Jones says he called police -- and when they arrived, they arrested the suspect.

On Friday, Jones scored a 1st round victory at the World Series of Fighting 23 event in Arizona.