7:42 AM PT -- TMZ Sports has learned ... both fans were ejected from the stadium following the incident.
We're told no injuries were reported ... and as it turns out, the guys knew each other.
No arrests were made.
A couple of Red Sox fans turned Fenway Park into their own Octagon during Monday night's game ... with two men getting into a violent altercation on the ground -- forcing security to get involved.
The incident went down as Boston hosted the Cleveland Guardians ... and it all seemingly got started over a beverage.
The person who posted the altercation claims the man in red spilled a drink on the fan in white ... which led to both guys duking it out on the stadium floor.
Just another Monday in Boston 🥰 #redsox #fenwaypark #fenway pic.twitter.com/ApJIxLsKqr
— kiers jenner (@kind_spice) July 26, 2022
The fan in white throws several punches as the man in red holds him down on the concrete ... before two security guards intervene and diffuse the situation.
No word on whether the guys were arrested -- the video cuts off as the guards swoop in and hold them back.
One fan is heard yelling, "let's f***ing go, woo!!" as the altercation unfolds ... with others watching the action in the distance.
The incident in the stands happened as the Sox pulled off a 3-1 win over the Guards ... which was their first win since getting pummeled in a 28-5 defeat at the hands of the Blue Jays on Friday.