Nicki made the announcement Friday on her "Queen Radio" show ... saying, "I think I have what I was striving for, just happiness. It was hard to get to a happy place. Now that I'm here I don't want to compromise that for anyone or anything."

The timing is interesting ... Nicki released a music video for "MEGATRON" earlier Friday, and it heavily featured her ex-con boyfriend, Kenneth Petty, and was met with immediate backlash, which she brushed off.

Nicki and Kenneth started dating last year after rekindling their flame ... and she says she's convinced he's matured from a checkered past that includes convictions for attempted rape and manslaughter.

It will be Nicki's first marriage.

Congrats!!!