Argentina's Juan Martin del Potro won a semi-final thriller against Spain's Rafa Nadal on Saturday, outgunning the Spaniard 5-7, 6-4, 7-6(5) in a nervy final set tie-breaker to advance to the Olympic singles final.
Del Potro will face Britain's defending Olympic champion Andy Murray in the final on Sunday.
Nadal, who won singles gold at the 2008 Beijing Games and has already captured gold in Rio in the men's doubles, will face off against Japan's Kei Nishikori for a bronze medal.
Earlier, Murray advanced to the men's Olympic final with a straight sets victory over Japan's Kei Nishikori on Saturday, securing a chance to defend his title and become the first player to win back-to-back singles golds at the Games.
In a commanding performance, the Wimbledon champion and number two ranked player broke Nishikori's serve early on, breezing through the first set 6-1. After another service break early in the second set, Murray closed out the match 6-1, 6-4.
Though Nishikori's speed allowed him to punch back against Murray's blazing ground strokes, the Japanese player was plagued by too many unforced errors and could not break Murray's serve.
