Steven Seagal -- Russian Fight Video Was Real ... I'm a Martial Arts Beast!!!

Steven Seagal is no martial arts fraud ... telling TMZ Sports that crazy Russian fight video that hit the web last month -- where he tossed around 2 dudes like rag dolls -- was 100% legit.

The fight footage showed Seagal reportedly teaching a "masterclass" at a martial arts event in Russia back in March ... but he's so dominant while spending minimal energy, it seemed his opponents were taking dives.

So, we had to ask Steven about it when we saw him at LAX Tuesday and he couldn't have put it more bluntly -- "I'm gonna try not to be insulted man, I've been doing martial arts all my life."

He went on to explain that when guys think their arms are about to snap ... they go down faster.

Bottom line -- don't mess with this guy. He'll break you.