Joe Rogan -- the voice of the UFC -- is taking a stand on transgender MMA fighter Fallon Fox ... saying there's "no f**king way" she should be allowed to get in the ring with a natural woman.
Rogan unloaded on Fox during his podcast, "The Joe Rogan Experience" -- saying, "She calls herself a woman but ... I tend to disagree."
He continues, "She used to be a man ... but now she has had, she's a transgender which is (the) official term that means you've gone through it, right? And she wants to be able to fight women in MMA. I say no f**king way."
"I say if you had a d*ck at one point in time, you also have all the bone structure that comes with having a d*ck. You have bigger hands, you have bigger shoulder joints. You're a f**king man. That's a man, OK?"
"I don't care if you don't have a d*ck any more," Rogan added ... "You're a man without a d*ck."