Monica Puig has won Puerto Rico's first ever Olympic gold medal after beating Germany's Angelique Kerber in the women's singles final.

Puig, 22, has never been beyond the fourth round of a Grand Slam competition with just one WTA title her name, but has caused a major upset in beating Australian Open champion Kerber 6-4, 4-6 6-1.

Kerber managed to haul back her opponent in the second set but was unable to match her intensity in the decider as Puig stormed to a commanding lead before breaking down in tears as she sealed a historic victory.

Earlier, Petra Kvitova of Czech Republic beat USA's Madison Keys in three sets to seal the bronze medal.

In the men's singles, 2012 champion Andy Murray will meet Juan Martin del Potro in Sunday's final after the Argentine came out on top in a gruelling encounter with Spain's Rafael Nadal, sealing a 5-7 6-4 7-6 (7-5) victory.

Monica Puig
Monica Puig of Puerto Rico reacts after defeating Angelique Kerber of Germany. Getty

Nadal had clinched doubles gold with Marc Lopez on Friday (12 August) but a demanding campaign in Rio took its toll in what was his 10th match of the competition. There was still time for one more fight back, however. With Del Porto serving for the match at 5-4, Nadal broke back to love after a stunning sequence of returns in front of perhaps the most animated crowd Rio has seen so far.

Third-set tie-breaks followed, but Del Potro held his nerve, sealing his place in the final when Nadal wide a forehand wide.

Del Potro, who won bronze at London 2012, has been forced to battle back from a series of wrist injuries that threatened to end his career.