Canelo Alvarez didn't let a hard-fought battle in the ring keep him from singing his heart out at the club on Saturday -- the boxing superstar hit up a Vegas club for some amazing karaoke after losing to Dmitry Bivol ... and TMZ Sports has the vid!!
Alvarez was in great spirits just hours after going up against the undefeated Russian boxer at Resorts World's Zouk nightclub ... singing along to Mexican hits like his go-to song, "Eso y Más" by Joan Sebastian.
This is pretty much a tradition at this point -- Canelo serenaded his wife, Fernanda Gómez, at the same club after he beat Caleb Plant back in November .