Luis Suarez netted a second-half double to secure a 2-0 victory over 10-man Peru and send Uruguay into the Copa America final.
Liverpool striker Suarez scored twice in five minutes shortly after half-time in La Plata to keep Uruguay's hopes of securing a record 15th South American title alive.
Suarez netted his first on 52 minutes after Peru goalkeeper Raul Fernandez spilled a speculative Diego Forlan shot.
The 24-year-old then ran onto a long pass, before rounding Fernandez, to roll in the simplest of second goals and seal a place in Sunday's final where Uruguay will meet the winner of Wednesday's semi-final between Paraguay and Venezuela.
Peru's night was further soured with skipper Juan Manuel Vargas shown a straight red card on 68 minutes after he elbowed Sebastian Coates in the face.
The teams had shared a 1-1 draw in the group stages. However, Uruguay always looked the more likely to progress to the final as the 14-times winners handled the occasion far better.
It did not take long for Uruguay to establish their threat and only their poor finishing cost them a first-half opener.
Suarez was the chief culprit in the first 45 minutes as he wastefully blazed over after Diego Lugano nodded down a Forlan free-kick while Alvaro Pereira shinned a glorious chance at Fernandez from close quarters.
Peru almost stole a goal against the run of play after 25 minutes when Vargas fizzed in a low cross that just evaded the outstretched legs of two attackers.
Uruguay responded by putting the ball in the net just before the break, only for the 'goal' to be chalked off after Pereira strayed offside to reach Lugano's flick-on.
Any frustration Uruguay had about reaching the break on level terms were quickly dispelled by Suarez as he displayed the predatory instincts that prompted Liverpool to pay £23million for his services in January.
He opened the scoring on 52 minutes when he was quickest to react after Fernandez failed to grasp Forlan's 35-yard drive, squeezing his shot in from a tight angle.
Suarez's finishing skills were then on show again soon after when he ran onto a long ball and coolly rounded the onrushing Fernandez, who was left exposed by his defence, before rolling the ball into the net.
Any hopes of a Peru recovery looked remote and they were made almost impossible by the indiscipline of their skipper Vargas, who inexplicably elbowed Coates in the face right in front of the referee.
Peru did almost pull a goal back when Muslera had to scramble to gather after he had mis-handled a fierce drive from Jose Paolo Guerrero, but Suarez's double was enough to send Uruguay into the Sunday's showpiece in Buenos Aires.