Gennady Golovkin's Endorsement Deals Are Exploding

He's quietly become one of the most dominant athletes on the planet -- but now Gennady Golovkin is finally cashing in outside the ring with HUGE endorsement deals, TMZ Sports has learned.

In fact, Gennady recently got into business with Apple and was just featured in a commercial for the Apple watch. According to his rep, it's the beginning of a growing relationship.

"It's an ongoing deal. They shot him for about 5 1/2 hours. They have a lot more content to come."

But Apple seems to be just the beginning for Gennady, whose stock has SKYROCKETED over the past year as he's knocked out opponent after opponent on his way to a 34-0 record.