Some of the fastest legs in sports are now also officially the coolest looking ... 'cause Robert Griffin III just completed a tattoo sleeve on his leg with pics of the Ninja Turtles -- and they're AWESOME!!
RGIII's leg art has been in the works for months -- he famously got Hulk and Goku inked on his left limb back in September -- but he was finally able to finish off the piece this past weekend.
We're told Griffin turned to Nic Westfall, the same guy who did the original artwork, to add on Teenage Mutant Ninja Turtles and a Black Panther piece .