Angel di Maria's goal gave Argentina its second Olympic football title in a row, a 1-0 victory over Nigeria on Saturday.
Di Maria collected a through ball from Lionel Messi in the 58th minute to give 2004 winner Argentina another gold medal and leave the Nigerians, champions in 1996, the silver.
Brazil won the bronze on Friday by beating Belgium 3-0 in Shanghai.
The only football game to be played in Beijing's Olympic stadium, Saturday's match was watched by a crowd of 89,102 but hampered by very hot conditions. The referee took the rare step of twice allowing players to stop and take drinks.