Ronda Rousey -- Not Preggo

Ronda Rousey is NOT with child ... despite rumors perpetuated by rival UFC fighter Cris "Cyborg" Justino, so says UFC prez Dana White.

Early Thursday, Cyborg went to Twitter and wrote, "I keep hearing the rumor @RondaRousey is expecting and no longer fighting #ufc205 if true congrats on the new life."

Ronda has previously talked about having children with her boyfriend, Travis Browne -- but never gave a time frame.

We spoke with White ... who tells us he talked with Ronda on the phone after the Cyborg tweet and she assured him it just ain't true.

Still no word on when she's expected to get back in the Octagon.