Michael Sam -- Hits the Club ... Single & Ready to Mingle (Video)

Michael Sam has returned to Hollywood ... hitting the club scene WITHOUT his ex-fiance ... and TMZ Sports has the video.

Sam was hanging out at Bootsy Bellows on the Sunset Strip on Saturday -- partying with NFL star Marcedes Lewis.

It's interesting ... considering Sam went M.I.A. for a while -- leaving his CFL football team for personal reasons last month right around the time things fell apart with his longtime BF Vito Cammisano.

But last night Sam was a single man on the prowl -- and partied like he didn't have a care in the world.

He should have one care though -- he hasn't played a single down for the Montreal Alouettes in their first 4 games this season.