Tom Brady Hits David Beckham Birthday Party

1:50 PM PT -- TMZ Sports has learned the mystery woman is ex-NHL player Tie Domi's wife, Heather ... and it doesn't sound like they're an item in the slightest -- considering the former Toronto Maple Leafs player was present for the bash, too.

Brady and Domi go back ... and they even hit the ice together in 2024, with TB12 playfully beating up the longtime enforcer during a workout.

Tom Brady appears to have a new love interest in his life ... the NFL legend took a brunette to David Beckham's birthday party over the weekend.

Gisele Bündchen's ex-husband hit DB's bash at the Cipriani Downtown Miami in Florida on Sunday with the mystery gal ... and while there were no public signs of PDA, it sure had all the makings of a date.

They showed up together, wore matching attire ... and walked in with some of Brady's pals. They were seen schmoozing a bit while inside the event too.

No word yet, though, on who she is or how they met.

Beckham's party, meanwhile, was a star-studded affair ... in addition to Brady, Shaquille O'Neal, Marc Anthony and Cindy Crawford all showed up to help the former soccer superstar celebrate his 50th.

Futbol superstars Luis Suarez and Lionel Messi were also there ... and Beckham -- who looked spiffy in a tux and bowtie -- sure seemed to appreciate everyone who turned out for his festivities.