Josh Allen's Ex-Girlfriend Stuns In Tiny Blue Bikini

Brittany Williams instagram

While Josh Allen's slated to wed Hailee Steinfeld in just a few weeks, the NFL superstar's ex has clearly been married to an amazing fitness routine -- check out some bikini pics Brittany Williams shared Monday, she looks goooood!!!

Allen's former girlfriend threw up the photos on her Instagram page ... showing off a taut physique to her nearly 150,000 followers.

Williams, wearing a small blue bikini, posed in front of the Pacific Ocean and a few mirrors ... while out in Pismo Beach with the dog she and Josh once owned together.

Obviously there was no mention of the Bills signal-caller anywhere in the post -- but one of Josh's former teammates' wives, Summer Allen,…