How do we know Michael Phelps is secure in his manhood? 'Cause he cried in public at the Super Bowl ... WITH HIS MOM ... and TMZ has the pics.

The greatest Olympian of all time -- who happens to be a die-hard Baltimore Ravens fan -- unleashed the waterworks at The Superdome in New Orleans on Sunday ... where he and his mother were cheering on their hometown squad.

The pics were taken right at the end of the game ... as the Ravens wrapped up their victory against the San Francisco 49ers ... and judging from the pics, Michael couldn't quite control his emotions.

Somewhere, Ray Lewis is smiling (and also probably crying).