Victor Ortiz -- Teaming Up with Ray J on Rap Song

Victor Ortiz and Ray J have more in common than the fact they both took part in fights last weekend in Las Vegas -- they're teaming up to do a song together.

TMZ has obtained a track from DJ Ian Carey, which features Ray J singing ... and a short rap verse from Ortiz.

The song is called "Baddest Girl" and Ortiz comes in around the 2:02 mark. Listen and judge for yourself ...