Floyd Mayweather partied all night after his victory, and it got so wild cops had to come and calm things down.

The champ showed up at his strip club, Girl Collection, in Vegas at around 2:30 am Sunday in the sickest new Red Bugatti.  

Floyd partied inside for 2 hours, then re-surfaced and dealt with Vegas cops who showed up for crowd control.  They were so many people who wanted a piece of Floyd they were spilling into the streets.

BTW ... it costs $500 a pop to get inside Girl Collection.  Floyd literally made money coming and going.