A former MMA fighter used his combat skills to open a can of whoop-ass on a knife-wielding assailant in self-defense... and the dramatic scene was caught on video.

Javier Baez drove back to his Miami apartment complex after a night out on Halloween ... and spotted Omar Marrero screaming and brandishing a knife in the parking lot, according to WPLG News.

After Baez parked his car, Marrero reportedly walked over and started hitting his window with the knife.

Marrero then opened the driver's side door and tried to slash Baez, who got out to dial down the escalating tension.

But it didn't work ... Marrero kept swinging the knife at Baez and retrieved a second blade from his vehicle nearby.

Baez wasn't intimidated, though, reverting back to his days as a Mixed Martial Arts fighter and making quick work of Marrero.

Check out the video ... Holding one of the knives, Marrero charges at Baez, who lifts him up and body slams him to the ground. Baez then disarms Marrero and puts him in a chokehold.

Baez later told a WPLG reporter, "Once I started putting the choke in, he kind of just let it go because no one is worried about anything else but breathing when you’re losing air."

Baez added, "I was able to hold him down with my knee and call the cops, and he woke up, cops came, and it was good, easy peasy!"