Fists were flying, beer was thrown and a dude got KICKED DOWN THE STANDS during a brawl at the NY Red Bulls game on Tuesday ... and TMZ Sports has the crazy video.
Sources in the stands tell us ... Red Bulls fans had been getting into it with Chivas Guadalajara supporters during the CONCACAF Champions League semifinal at Red Bulls Arena in NJ all game long.
But, things finally came to a head after time expired when the smack talk turned physical.
You can see beer flying from everywhere -- including people from the upper level showering the fighters below them.
The craziest moment ... one of the combatants kicked another dude right in the chest -- sending him flying backwards down several rows of seats.
Stadium security eventually showed up and broke up the violence -- but you can see several people had already suffered injuries by the time help arrived.
We've reached out to the Red Bulls and stadium security -- so far, no comment from anyone.
By the way ... the game ended in a 0-0 tie.