Canelo Alvarez wants to open a can of whoop-ass on Lionel Messi -- the boxing superstar blasted the Argentinian striker for seemingly disrespecting his home country after defeating Mexico in the World Cup.
Canelo's rage stems from a viral video of Messi celebrating with his teammates after Saturday's 2-0 win ... which shows a Mexico jersey lying on the ground near his feet.
Some -- including Alvarez -- believed Messi was intentionally displaying his contempt for El Tri ... as he appears to kick the jersey in the video.
The super-middleweight champion went to social media to call Messi out over the whole thing ... saying, "Did you see Messi cleaning the floor with our jersey and flag???"
"He better pray to God that I don't find him!! Just like I respect Argentina, he has to respect Mexico!"