Boxing superstar Victor Ortiz has been hit with a lawsuit by the guy he allegedly beat down at a Kenny Chesney concert ... but Ortiz claims the accuser was too damn drunk to remember what REALLY went down that night.
In court docs obtained by TMZ Sports ... the accuser claims Victor and his brother were bouncing around the Rose Bowl on July 25th looking to pick a fight while a Rose Bowl security guard egged them on.
The accuser claims he was going to get food and drinks for his fiancee ... when out of nowhere, and for no reason, the Ortiz brothers coldcocked him and beat him down until he was unconscious.
In the suit, filed by attorney Cynthia Hafif, the man claims the security guard recorded the whole thing on his phone.
Ortiz and his brother were both arrested and charged with battery. Now the victim wants them both to pay up. He's also suing the city of Pasadena which owns and operates the Rose Bowl.
But Victor's lawyer, Mark Davis, says the accuser is lying -- telling TMZ Sports HE was the real bad guy ... and had been drunkenly trying to pick a fight with the Ortiz brothers. Davis claims the accuser took the first swing.
Victor's attorney says the lawsuit is just a shameless money grab ... and "when the facts are out Victor will win both the civil and criminal case."