Caitlyn Jenner -- My Boobs Got More Action ... Than the WNBA

Caitlyn Jenner's breasts defied the odds last night ... and people won a TON of money because of it ... this according to the gambling site that put up a prop bet on CJ's cleavage.

As we previously reported, BetOnline.ag offered gamblers the chance to bet on whether Caitlyn would show off the gals during the ESPYs -- and before the show, the odds said she would.

But while CJ flaunted a plunging neckline when receiving the Arthur Ashe Award for Courage -- there was NO CLEAVAGE -- so the website says it did NOT pay out for pro-boob bettors.

Surprisingly, the site says 78% of bettors put their money on "no" -- so the public wins thanks to Caitlyn's classy fashion choice.