Tom Brady Gets 'Happy Birthday' Serenade at Patriots Training Camp

Tom Brady is turning the big 4-1 Friday ... and Patriots Nation is throwing the QB a massive birthday bash in New England complete with a giant cake, a balloon animal Tom Brady ... and a birthday song!

It all started when TB12 jogged out to the field --the crowd went crazy and then busted out the song. Brady smiled and waved at the fans.

Off the field, there was a giant #12 birthday cake and a giant #12 birthday card for fans to sign.

But, the best part ... was the life-size "Balloon Brady" ... which was put together REALLY WELL by a person with better than average lung capacity.

Brady also got some love from his wife, Gisele Bundchen -- who posted a love note to her hubby on social media ...