Blanket Jackson Is Black Belt in Karate!!!

Michael Jackson's youngest son isn't a little kid anymore ... and he's armed and dangerous.

Blanket Jackson is now 15, and he's a black belt in Karate. He was leaving an L.A. martial arts studio Saturday strutting his stuff.

FYI ... a black belt with a white stripe is the Master Black Belt designation in karate.

It's pretty amazing ... all 3 of Michael's kids have emerged from the shadows and found their path.

Short story ... Blanket's still not old enough to drive, but he moves fast.