L.A. Kings Fans Get In Insane Brawl, Shirtless Haymakers & Popcorn Showers!

Here's one of the craziest and most violent in-arena brawls EVER -- courtesy of some fans at Thursday night's L.A. Kings game.

The hometown squad was in a tight matchup with the Florida Panthers ... when one witness tells us he noticed a fight beginning to break out in the Staples Center lower bowl.

You can see in the video what happens next ... a scrap escalates into AN ALL-OUT BRAWL!!

The scene is insane ... there's a woman throwing a FLURRY of right hands to start -- and then things get even crazier.

A shirtless man runs into the scrum with a flying left haymaker ... and then for some reason, a fan dumps popcorn all over the action!!!

It's all followed up by some more punching, pushing and shoving ... before in-arena security is FINALLY able to break it up.

We reached out to our law enforcement sources ... and they tell us it appears no one was arrested ... and say Staples security usually handles this on their own by ejecting fans.