Nicole Murphy -- I Can Still Shake My 46-Year-Old Ass ... LIKE A CHAMP!

Michael Strahan's fiancee proved he's a lucky man Wednesday night at a karaoke bar in Malibu -- by showing off her serious ass-shaking skills and putting young hotties to shame.

Nicole Murphy popped her booty to "Pony" by Ginuwine at Cafe Habana with co-stars Shamika Lawrence and Mayte Garcia ... and the other "Hollywood Exes" were clearly not in her league.

The trio attempted to sing "Hold On" by En Vogue as well (video below) ... but there's a lot less butt shaking.

Our apologies.