Andy Murray has defeated Juan Martin del Potro in four sets to win his second Olympic gold medal.

In a classic that lasted over four hours, the British number one prevailed by a 7-5 4-6 6-2 7-5 scoreline to match his achievement in London four years ago.

At a time when Murray is looking to add Grand Slam titles to his collection, he has always stressed that retaining his Olympic title was one of his biggest priorities of 2016 and that showed during an exhilarating final played in a partisan atmosphere in Rio de Janeiro.

A tense opening set lasted 74 minutes but after letting slip a 4-1 advantage, Murray broke Del Potro for a third time to move ahead in the best-of-five final.

However, Del Potro struck at the start of the second and he started to show the kind of form that had seen him defeat both Novak Djokovic and Rafael Nadal earlier in the tournament.

Saturday's win over Nadal had lasted more than three hours and it appeared to be taking its toll on the Argentine as Murray eased back into the lead to move closer to a historic triumph.

Back came Del Potro, though, and after they had exchanged breaks of serve at the start of the fourth, Del Potro gave himself the chance to serve out the set and set up what would have been the most dramatic of deciders.

Determined to avoid another hour on court, Murray broke back to level and in Del Potro's next service game, he struck on his second match point to cap off an exhausting week that has twice seen him edge last-set deciders with Fabio Fognini and Steve Johnson.

For Del Potro, he will take the positives from what has been a fairytale week after his much-documented wrist problems but he will have to endure the disappointment of failing to claim gold in front of a passionate South American crowd.