Saints Star -- Mardi Gras PARTY with Super Bowl Ring

Sources connected with the party tell TMZ, Pierre wasn't just celebrating Fat Tuesday -- the guy just signed a 4-year $12,000,000 contract extension last week ... and wanted to let loose with his teammates.

We're told the party -- which went down at Metropolitan nightclub in The Big Easy -- featured 8 DJs, 2 dance floors, a dessert bar, and 15 go-go dancers ... not too shabby.

We thought it was bad luck to wear your Championship ring all the time -- but clearly, that theory doesn't hold water.