The Game Locks Undies Deal and it's HUGE for Charity

The Game's penis is giving back ... and not just to millions of his thirsty fans on social media.

After Ethika sales soared from Game's big revealing Instagram posts ... the underwear line and rapper got to work on a new line of briefs, specifically for a deal with the rapper.

We got the first pics of the collection (junk-free, sorry) which will benefit Game's charity, The Robin Hood Project. We're told for every pair of the drawers sold, one will be donated to a homeless shelter.

The collab was pretty inevitable since sales spiked 500% after Game's selfie went viral.

Game's also promising a surprise for all paying customers. Here comes more junk.