Tom Brady is supporting Rob Gronkowski ... 's junk -- the future Hall of Fame tight end is modeling Brady Brand underwear while showing off his ripped bod!!
Gronk -- who won 4 Super Bowls playing alongside Tom -- is reconnecting with the G.O.A.T. once again ... showing off some undies from TB12's apparel brand alongside his stunning girlfriend, Camille Kostek.
"Brady to Gronk once again, this time off the field with a @bradybrand underwear pass! I sure scored after that play hehe! Gronk wrote on social media.
In the pic, 33-year-old Gronk and Kostek are wearing all white underwear ... and judging from the pic, Gronk's abs look like he's ready for an NFL comeback!!
Gronk retired for a second time earlier this offseason ... leaving 45-year-old Brady to try to win an unprecedented 8th Super Bowl ring without one of his most trusted targets.