Jon Cryer -- Helmet Saved My Life During Bloody Bike Crash

Moments after his gnarly bike crash this weekend, a battered Jon Cryer credited ONE THING with saving his life -- his bike helmet -- claiming he could've been killed ... if not for the protective headgear.

The "Two and a Half Men" actor withdrew from Sunday's Nautica Malibu Triathlon due to his injuries -- which he proudly shows off in the video -- and on his way off the course, a still-bloody Cryer pointed to his helmet and said, "Thank God for this bad boy."