Peralta struck after just 30 seconds and the Mexican striker sealed one of the all-time great Olympic upsets when he scored again late in the second half. Hulk got one back in stoppage-time but Mexico, playing in their first Olympic final, were deserved winners as Brazil once again failed to end their long wait for a first football gold.
On Friday, South Korea's men beat fierce Asian rivals Japan 2-0 in the play-off for bronze to claim the country's first ever Olympic football medal. Japan were bidding to emulate the Japanese team of 1968, who won bronze at the Mexico Games, but despite enjoying more possession, the Asian champions were twice unpicked by their opponents' clinical counter-attacks.
Arsenal striker Park Chu-Young and captain Koo Ja-Cheol scored either side of half-time, as the Taeguk Warriors claimed a measure of revenge for the senior side's penalty shoot-out loss to Japan at last year's Asian Cup.
But South Korean’s victory hit a controversy when the International Olympic Committee asked them to bar a player from Saturday's medal ceremony after he was photographed apparently holding a political message about a territorial dispute with Japan following their bronze play off. Midfielder Park Jong-woo, who held up the sign after his team's 2-0 victory over Asian rivals Japan on Friday, risked inflaming an already tense political situation between the countries. They have long argued over the islands which are known as Takeshima in Japan and Dokdo in South Korea, and which lie equidistant from the two nations.
While Brazil have graced the World Cup with some of the best players and most dazzling performances ever seen on football's grandest stage, the Selecao have never managed to replicate those golden moments at the Games and this was another miserable chapter in their Olympic history. Brazil, bronze medallists in Beijing in 2008, lost in the Olympic final in 1984 and 1988 and their failure to win gold has rankled with such a proud football nation for decades. Mano Menezes's team are unlikely to get a sympathetic reception on their return home after such a lacklustre display riddled with nerves and defensive blunders. From Rio to Sao Paulo those unconvinced by Menezes had already begun to whisper that former Brazil coach Luis Felipe Scolari should be installed in time to lead the nation's bid to win the World Cup on home soil in 2014 and those calls will get even louder after Mexico's giant-killing act.
After sweeping to the final with five successive wins, Brazil were heavy favourites and Mexico's chances looked even slimmer when Tottenham striker Giovani dos Santos was ruled out with a hamstring injury suffered during the semi-final win over Japan. But the Mexicans had won three of their past five matches against Brazil, including a 2-0 friendly victory in June, and there was no sign of an inferiority complex as Luis Fernando Tena's side made an astonishing start.