Guy Fieri got into a nuclear fight with his hairdresser Saturday ... and it was caught ON VIDEO.
The video -- obtained by TMZ -- shows Ariel Ramirez punching Guy through the open door of the SUV, swearing at him. You also see Guy kicking him. Ariel is so mad, he cries uncontrollably during the fight.
Although you don't see how the argument ends, we're told Guy threw Ariel out of the SUV. Guy's manager then jumped out and he took Ariel home by cab.
Sources close to Guy tell TMZ ... They were coming from San Francisco International Airport, where they had just landed. We're told they had all been drinking on the flight and used a car service to take them home.
As for how the argument happened ... we're told it was about nothing. One source said, "It was just dudes being dudes." It escalated into a physical fight.
A rep for Guy tells TMZ, "A bunch of guys were messing around. Things got a little out of hand, but they're all good now."