Usain Bolt -- Smoking the Competition ... in Cali Weed Shops

Potheads have a new reason to cheer for Usain Bolt ... besides the whole Jamaica thing ... TMZ has learned California weed shops are now selling a strain of weed named after the fastest man on the planet. What an honor!!

Our well-informed, and prescription-carrying sources, tell us ... ever since the Games began, multiple weed dispensaries in the Orange County area have been selling a new product called, "Usain Bolt OG."

One pot shop honcho tells us U.B.O.G. got its name because it's so "fast-hitting" ... get it? Stoner humor ...

But the Olympic weed tie-ins are far from over ... we're told some shops plan to release a new line of weed-filled baked goods inspired by U.S. Judo fighter Nick Delpopolo ... who was just booted from the Games for eating a pot brownie.

Silver lining?