Gold medalist Michael Phelps showed off a new trophy in his hometown of Baltimore the weekend of Oct. 2 — his girlfriend.

And it sounds like the 14-time gold medalist is diving into this relationship head first!

He even took the stunning brunette, who OK! can reveal is 2007 Miss California runner-up Nicole Johnson, to meet his mom, Debbie.

"Nicole’s been around for a while," says a pal of Michael.

Nicole accompanied Michael, 23, to his Oct. 4 homecoming parade before joining the swimming champ and 20 family members and friends at Morton’s The Steakhouse, where he feasted on an Olympic-sized 14-ounce filet, creamed spinach, iceberg salad, green beans, mashed potatoes and a dessert trio.

Michael asked the server for change, an insider tells OK!, explaining that "it was for his girlfriend to pay the valet."