Sly Stallone -- Boxer Earns Role In 'Creed' ... After Brutal Real-Life Fight

This is a pretty great story ...

A real-life pro boxer earned himself a role in Sylvester Stallone's upcoming "Creed" movie ... all because producers were super impressed with the way he fought during a FEROCIOUS 2014 bout.

The guy who battled his way on to the big screen is Hammerin' Hank Lundy -- who happened to be fighting on the undercard of a Gabe Rosado fight back in December.

Turns out, Rosado had already been cast for a role in the film -- and producers decided to check out the fight in person in December to see their new star in action.

Lundy was taking on a guy named Thomas Dulorme that day ... and their fight was EPIC -- with the two men slugging it out for all 10 rounds.

Lundy lost the fight -- but producers LOVED the way he fought ... and hooked him up with a role in the flick.

When we saw Lundy in L.A. yesterday, he recapped the story ... and couldn't be happier about the way things turned out.

Pretty cool, right?!