Oribe Peralta's stunning 64th minute strike was the catalyst to guide Mexico past a spirited Japan side and into Friday's gold medal match.
Substitute Javier Cortez added a third deep into stoppage time to put the gloss on the semi-final result.
It completed an excellent comeback for Mexico whose appearance in a first Olympic final in their history was under threat following Yuki Otsu’s first half blockbuster for Japan.
But Fabian’s glanced header levelled affairs before Peralta’s sweet strike and Cortez’s late finish proved enough to send the Mexican fans into a state of delirium.
Both sides had remained undefeated in their run to the semi-finals and the coaches’ starting line ups reflected those superb performances.
Luis Fernando Tena named the same starting eleven that thrillingly beat Senegal 4-2 after extra time in the quarter final.
The Mexico team has been a model of consistency, not just through their results, but also with their starting line up with eight of the eleven playing every game so far in the tournament.
Takashi Sekizuka also named an unchanged side following Japan’s crushing 3-0 win over Egypt in their quarter final. Top scorer Kensuke Nagai recovered from a slight knock to take his place in the starting line-up.
With both teams relying on compact, disciplined foundations in progressing through the tournament, it was a surprise that the match kicked off with an open feel to it; both looking sprightly and inventive on the ball.
Chances came at a premium though with both teams limited to long range sighters. First of all Peralta dragged a shot off target for Mexico after a dangerous run from Giovani dos Santos before Kiyotake came even closer for Japan fizzing a drive inches wide of Corona’s right hand post.
Indeed, it was through such a long range effort that brought a sensational opening goal for Japan.
Neat build up play eventually led to the ball being played into Yuki Otsu. The midfielder took one touch to set himself before crashing an unstoppable right footed shot into the top left hand corner from fully 25 yards.
The stunning strike was Otsu’s third goal of an impressive tournament and seemed to settle the Japanese into a steady, attractive passing rhythm.
In contrast, Mexico looked rattled; too often harried and rushed into lackadaisical possession by a well drilled Japanese outfit.
To their credit though, Tena’s side started to work their way back into the game with Japan’s remarkable record of not conceding throughout the Olympics perhaps at the forefront of their thinking.
Fabian tested Gonda with a scuffed shot after twenty minutes before Dos Santos was brilliantly tackled just as he was about to pull the trigger.
The Tottenham winger then had Mexico’s best chance of the game but could only bend his shot wide when a cross broke to him on the edge of the penalty area.
And Mexico’s increasing pressure finally paid off in the 28th minute to become the first side to breach Japan’s impregnable defence. A right wing corner was flicked on at the near post and Fabian glanced his header into the far corner to haul his side onto level terms.
It was Japan’s turn to be rattled as Mexico broke quickly a minute later to feed Dos Santos down the left side of the penalty area. The 23-year-old got his angles all wrong though, chipping harmlessly over Gonda’s crossbar.
The South American outfit were starting to spray their passes around with improved confidence and accuracy and Japan were struggling to cope - their early domination of possession a fading memory.
The rest of the half was played out with little further incident though, with Mexico ending the first 45 minutes on top after Japan’s early flurry.
The start of the second half was reminiscent of the first, with Japan quickly onto the front foot.
And the first real chance fell their way with Takahiro Ohgihara seeing his shot blocked before the rebound was driven well over the bar by Nagai when he should have hit the target.
It was the only early chance of a decidedly scrappy second half with both teams pressing and probing with little to show for it.
That was to change shortly after the hour mark when Mexico took the lead through another spectacular long range strike.
Gonda had initially saved Oribe Peralta’s snatched shot but following the goalkeeper’s throw out, defender Ogihara dallied on the ball for far too long.
Peralta nicked the ball off him, before bending a wicked 25 yard shot beyond Gonda’s despairing dive to put Mexico within touching distance of the final.
Japan immediately upped the tempo and proceeded to lay siege to the Mexican goal, throwing in cross after cross, but to no avail.
Mexico comfortably held out and looked dangerous themselves on the counter attack as Japan failed to create any clear cut chances in retaliation, seemingly lacking any concerted urgency to pull themselves level.
And it was from such a counter attack that substitute Cortez was able to drive into the Japanese penalty area before dispatching a low drive past Gonda.
Seconds later, Gianluca Rocchi blew the final whistle to signal Mexico’s first showing in an Olympic final where they’ll face Brazil or South Korea.
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