Diddy vs. Drake -- Nightclub Brawl All About R-E-S-P-E-C-T

It was money, not women, that made Diddy punch Drake outside of a Miami nightclub early Monday morning ... TMZ has learned.

According to our sources, Diddy confronted Drake just outside LIV nightclub -- where they'd both been partying -- and the topic of conversation was business. During the tete-a-tete, voices were raised and according to eyewitnesses ... Diddy said, "You will never disrespect me" ... and then clocked Drizzy.

Our sources say it was just the one punch -- Drake was stunned, but not knocked out. One report said the fight was over Diddy's girlfriend, but we're told that wasn't the case.