Floyd Mayweather Jr. -- Got Pissy Over Bathroom Incident ... Woman Alleges

A woman in NYC tried to stop Floyd Mayweather Jr. from going #1 ... then dialed 911 to complain the boxing champ got aggressive with her -- but we've learned she's got zero case.

Law enforcement sources tell TMZ Sports the barely alleged atrocity went down inside Saks Fifth Ave in NYC Wednesday night where Floyd was doing some holiday shopping. We're told he decided to go to the bathroom, but because there was a private event on that floor of the store -- a woman blocked him from entering the restroom.

Let's face it ... Floyd's quicker than the average bathroom attendant -- and was able to dip past the woman to get inside and get some relief.

According to our sources ... the woman immediately called cops to report Floyd for "calling her a bitch." Police took down a harassment report, but since the alleged offense didn't happen in front of an officer ... she's SOL. Case closed.