Canelo Alvarez Down To Box UFC's Jorge Masvidal, 'Why Not?!'

Forget Conor McGregor ... Canelo Alvarez says he's down to fight UFC star Jorge Masvidal next -- telling TMZ Sports, "Why not?!"

... Of course, in boxing only.

Masvidal famously called out Canelo shortly after beating Nate Diaz for the 'BMF' belt back in November ... and when we asked Alvarez out in L.A. this month if he'd be up for the fight, the boxing superstar told us he's down.

"For business, why not?!" Canelo says.

Neither guy has an opponent lined up for their next fight ... so could it actually happen??

Seems there's a chance ... the first big, MMA-boxing crossover was HUGE -- with Floyd Mayweather and McGregor making SERIOUS bank for getting in the ring back in 2017.

And, Canelo DEFINITELY appears pretty intrigued by that.

As for if the Masvidal fight falls through ... Canelo says he'd be up for a rematch with Mayweather next -- telling us, "I was very young and experienced at the time and now I'm a different fighter. It will be a totally different result."