Mexico beats Brazil 2-1 to win the gold medal in soccer at the London Olympics.

LONDON —Mexico is celebrating its first Olympic gold medal in men’s soccer  with a lively 2-1 victory over Brazil at Wembley Stadium on Saturday, and Brazil is wondering if it will ever be able to add the title to its long list of triumphs.

Oribe Peralta scored the first goal of the game just 28 seconds in, then added a second 15 minutes from full time to set off a wild and raucous celebration from the Mexican fans who have craved this kind of global success for so long.

For Brazil, there was only anguish and, understandably, no small measure of shock. The Brazilian team was loaded with stars. Many of their players are already playing club soccer for top teams like AC Milan, Manchester United, Inter Milan and Real Madrid. Others, like Neymar, who still plays in Brazil, are coveted by teams worldwide.

By comparison, the Mexicans had only one player on their roster who did not play in the Mexican league and that player — the top forward Giovani dos Santos, who plays for England’s Tottenham Hotspur — was injured in the semifinal and could not even play.

It did not matter. Mexico, which has suffered difficult defeats in previous forays deep into international tournaments, was the better team throughout. This victory will not erase the painful memories of matches like the 1986 World Cup quarterfinal loss to Germany on home soil, but it will be hailed by most Mexicans as the biggest victory in the national team’s history.

In Brazil, on the other hand, the predominant emotion figures to be bitter disappointment. The Brazilians were heavily invested in winning this tournament and earning the country its first Olympics gold medal in soccer — a conspicuous hole in the national team’s long list of accomplishments.

With those stakes — not to mention Britain’s abiding passion for soccer — a sellout crowd of 86,162 packed Wembley on a sunny afternoon, giving the match a feel not often associated with Olympic soccer. The Olympic tournaments — especially on the men’s side where all but three players must be under 23 — typically lack for attention, but at the London Games it has been different.

Two days after the United States women’s team beat Japan for the gold medal in front of a sellout crowd, Brazil and Mexico played a final that felt like a showpiece event.

For Brazil, the pressure on Coach Mano Menezes was undeniable. While most countries used a youth national team coach to guide their squads here, Menezes is Brazil’s senior national team coach, and the team he brought here is a reasonable approximation of the group Brazil is likely to offer in 2014 when it hosts the World Cup.

Even more, the players were well aware of the country’s Olympic misfortunes. Brazil last played in the final at the 1988 Games, losing to the former Soviet Union, 2-1. During this tournament, players like Neymar and the captain Thiago Silva spoke often of knowing the opportunity in front of them: Legends like Romario and Ronaldo never won gold. To deliver the country’s first Olympic title, Neymar said at one point, “would be a great honor.”

Mexico, meanwhile, was just looking for its first significant title. While soccer’s governing body recognizes Mexico’s 1999 win in the Confederations Cup as an international championship, to many observers, this was seen as a much bigger opportunity.

It certainly appeared that way from the start. Mexico has had uncommon success against Brazil in the past, winning 6 of the past 12 matches between the teams since 1999 (including that Confederations Cup final), and it was clear that Mexico was not intimidated by the Brazilians collective pedigree.

Just half a minute into the game, Mexican midfielder Javier Aquino pressured the Brazilian defender Rafael, who tried to slide a quick pass backward to escape. Peralta quickly read the play, jumped in front of the pass and smashed a shot past Brazilian goalkeeper Gabriel. Before most of the Brazilians had even touched the ball, they were down a goal.

Mexico continued to press the game through much of the first half, though halftime seemed to come at a perfect time as Brazil was starting to surge just before the break. Still, the Brazilians — who had scored three goals a game in their five matches leading to the final — struggled to find fluidity and squandered their chances in front of goal. When Peralta scored again in the 75th minute, firmly heading home off a free kick cross from the wing, Brazil’s hopes were essentially squashed.

There was a moment or two of tension from Mexico at the end, as Hulk managed to pull a goal back in the first minute of added time, but two minutes later — after one more miss from Oscar — the referee Mark Clattenburg blew the final whistle and sent Reyes and Neymar to the ground for very different reasons.

One was despondent that he could not be part of making history. The other was absolutely delighted that he had.