Canelo Alvarez has hands like cement and apparently a voice like a baby angel -- 'cause after the boxer beat Caleb Plant in the ring Saturday ... he showed off his amazing pipes at a nightclub!
Alvarez hit up Zouk in Las Vegas to celebrate his big TKO win ... and at some point during the party, he grabbed the mic from Zedd and blessed the packed crowd with an impromptu singing performance.
The star boxer belted out "Eso Y Mas" -- a popular Mexican love song by Joan Sebastian -- and it was great!