Peyton Manning -- The G.O.A.T. ... at Retirement Parties (PHOTO GALLERY)

Peyton Manning's retirement party went down in Bev Hills Monday night, and HUGE celebs showed up to officially send off the Super Bowl champ.

Justin Timberlake and Chance The Rapper were among the non-football stars at the Montage hotel ... and, of course, little bro Eli Manning was there too. But most of the guests were old teammates and coaches, like Von Miller, Marvin Harrison, Edgerrin James and Mike Shanahan.