Patricio Manuel began his paid career at the weekend on a high-profile Golden Boy Fight Night at Fantasy Springs.
Formerly Patricia, and a successful female amateur, Manuel entered the 2012 Olympic Trials but was forced out through injury.
Now 32, Manuel has made history as the first transgender boxer to win a professional contest on United States soil.
Transitioning in 2014, Manuel fully completed augmentation surgery in 2015 before initially competing as a man in 2016.
Scoring a victory over four rounds, Manuel defeated Hugo Aguilar on the cards but shockingly was greeted by some boos from the crowd.
“I hear some fans aren’t happy. It’s okay, I’ll be back. I’ll make you happy then,” said Manuel after the contest.
“I’ve got some naysayers out there that I need to prove that I deserve to be here. I’m not in here just for one show in one fight.
“This is something I love. I’m not done with this sport and I will be back.
“It’s a funny thing when just living your truth becomes historic.”
Manuel added: “Everyone who has been along for this journey over the past six years, really. Thank you so much, I couldn’t be here without you. I really needed that support to help push me to this point.
“There’s a lot of people behind my corner, my coaches, my beautiful partner, my family and friends and fans. There are so many people who wanted me to be here and I’m so glad I was able to perform for them.”
The historic triumph has opened the door for ex-females to compete as men. Although the same cannot be said of former men attempting to fight in the women’s ranks.
Hormone levels have to be kept under tight control following instances of severe injuries to women when facing transgender opponents in the past.
Like athletes, female competitors face stringent checks before being allowed to fight.