Rob Gronkowski just bid farewell to his BFF Tom Brady with a video and a mushy note ... and it ain't hard to see the tight end REALLY loved his quarterback.
Gronk posted it all to his social media page on Wednesday -- just one day after Brady announced he's done with football -- and it's probably the sweetest goodbye message Tom's gotten so far this week.
Rob shared a nearly two-minute video (set to Queen's "You're My Best Friend") that had a whole bunch of cool highlights of the two on and off the field.