Defensive resolve has carried the Jaguares to a 21-16 win over the Chiefs in Buenos Aires and booked them a historic berth in the Super Rugby semi-finals.
The South American side are through to the final four for the first time since their introduction in 2016, holding firm in a tense quarter-final on Saturday (AEST), willed on by desperate supporters at Jose Amalfitani Stadium.
A semi-final will be staged there next week, with either the Brumbies or Sharks forced to travel from Canberra after their Saturday night quarter-final.
It will be a stiff task to overcome a Pumas-laden side who qualified second for the playoffs via winning nine of their last 10 games, and have made a habit of strong finishes.
Down 10-8 at halftime, and 16-8 with half an hour to play, the Jaguares found a second wind which the Chiefs couldn't match.
Winger Matias Moroni completed an excellent team try which five-eighth Joaquin Diaz Bonilla converted, followed by two penalties.
The home side defended staunchly over the scoreless final quarter, aided by the Chiefs' shonky lineout and poor handling.
It ends courageous campaign from the Chiefs, who lost their first four games and overcame a crippling injury toll to scrape into the finals ranked seventh.
They will farewell their talismanic forward Brodie Retallick for the next two seasons, after the All Blacks lock negotiated a sabbatical to Japan.
Since winning twin titles in 2012 and 2013, the Chiefs have never failed to reach the playoffs but the final has always eluded them.
They were on the backfoot early, when a turnover gifted a try to excellent Jaguares flanker Pablo Matera with just 48 seconds on the clock.
It was 8-0 before the Chiefs flanker Lachlan Boshier bagged their only try, set up by a break from halfback Brad Weber.
Three penalty goals either side of halftime completed a run of 16 unanswered points before the visitors ran out of puff against more desperate foe.
Tries: Matera, Moroni
Cons: Diaz Bonilla
Pens: Diaz Bonilla 3
Pens: Debreczeni 2, McKenzie