One day after Iggy Azalea publicly confirmed her relationship with NFL star DeAndre Hopkins ... Iggy is taking it back -- now saying she's very much single.

Iggy was a guest on Y100 radio in Miami on Wednesday and played a game of "Truth or Dare" -- where she was asked if the rumors about dating the Houston Texans WR were true.

"Yeah, we're in a relationship," Iggy said.

But, hours later, Iggy went on Twitter and shut down ... herself ... saying, "I'm single."

"I have come to the conclusion i am going to be alone forever. I am completely fine with that. I have a routine now. I watch movies alone in the shower n s**t ... its nice."

So, what happened? We're workin' on it.

UPDATE -- DeAndre has now chimed in as well ... confirming the two are definitely NOT an official thing.

"Ya'll know I'm not a social media seeker but ya boi in SINGLE!!"

Which once again begs the question ... what the hell happened???