PHOTO: Ray-J COMPARES FAN TO AN APE (See PHOTO)

Ray J just pissed off millions of people -- one woman in particular -- after he compared her to a character from "Planet of the Apes."

Ray J Instagrammed the above photo Friday, writing the caption, "I usually don't go this hard but ... This chick look exactly like a character on Planet of the Apes."

He has since deleted the post -- but the fan he targeted (a woman named Tina Chastang) tells TMZ, she was mortified when he singled her out on his page.

In fairness, Tina admits she egged Ray J on a little, posting inflammatory comments on his Instagram like, "Ray J you are irrelavant. Why dont you stop worry about Kim Kardashian. Why dont you talk about you being gay." But she insists he didn't fight fair.

Tina tells us, she's just one voice out of millions of fans -- thousands of whom trash talk Ray J on the daily -- but he made a mockery of her on a global scale. Tina wants an apology.

Sources close to Ray J tell us, "This girl is an Instagram bully. She's been making negative comments on everything Ray J posts for months. He's been trying to take the high road, but finally decided he needed to give her a taste of her own medicine."