'Big Brother' Transgender Houseguest -- I'm Gonna Be Another Caitlyn!

Audrey Middleton, who will be one of the houseguests on the upcoming "Big Brother," was not always Audrey ... she was born Adam.

TMZ has learned Audrey will become the first transgender on the U.S. version of the show, and she plans to use the program as a showcase ... similar to what Caitlyn Jenner has been doing.

Audrey grew up in a small Georgia town as a boy, and life was far from easy. We're told when she transitioned several years ago, her family had a hard time accepting it, but they're now fully supportive and on board.

The 25-year-old was inspired by Caitlyn Jenner's story, but she's also just a big fan of "Big Brother."

It's a dicey move for producers, given the show has had its share of racist and homophobic houseguests. The show runs a livestream 24/7 and things happen. But we're told it will all become a teaching moment and Audrey is pumped.