Argentina have humbled Wales 26-12, 11 years to the day after its only previous victory at Millennium Stadium over the Six Nations rugby champion.
The Pumas dominated territory and possession and showed far more ambition as they scored the only two tries, coming from 12-6 down with less than half an hour to go.
Wales was limited to penalty goals, paying the price for aimless kicking and poor choices in attack in the face of a Pumas defence sharpened by their inaugural Rugby Championship campaign. They'd gone seven tests without a win since June.
"This is a great win for us," said captain and No 8 Juan Martin Fernandez Lobbe, the undisputed man of the match. "We've been searching for this win for a long time as a new group."
The scoreline flattered the Welsh, who edged a scrappy first half by taking their few scoring chances, then were over-run in the second spell.
Argentina first five Nicolas Sanchez, the backup kicker, converted three goalkicks and two dropped goals, nailing only half his shots in both categories. The Pumas scrum warmed up slowly and took a tighthead. And both wingers' tries were highlights.
In a surge up the middle from halfway, flanker Juan Manuel Leguizamon offloaded to Fernandez Lobbe with winger Juan Imhoff on his right shoulder. Imhoff, in space, cut inside Wales fullback Leigh Halfpenny and scored between the posts in the 55th minute. Argentina, leading for the first time in 40 minutes, was not headed again.
Sanchez converted for 16-12, and again five minutes later to Gonzalo Camacho's try. The Pumas pack rumbled back into Wales' 22 and Camacho was on the end of some one-handed catches to stretch out in Halfpenny's tackle to score in the right corner.
Sanchez capped the scoring with his first penalty, and Argentina held out for its first win over Wales in six years.
"This reaffirms what we are trying to do," Fernandez Lobbe said. "We are so happy to win against such a great team."
Even in the scrappy first half, Argentina showed a willingness to attack the line and made the only line breaks. Wales was opportunistic, and wasn't helped by game-ending injuries to centre Jamie Roberts, who suffered a head knock, and lock Alun-Wyn Jones, who left holding his left hand after conceding two penalties in the last minutes of the half.
But the Pumas also were dealt a blow, when veteran Felipe Contepomi, their all-time leading point-scorer, was taken off on a stretcher in the 14th minute after kicking a penalty when a ruck rolled onto his right knee and twisted it badly.
Argentina 26 (Juan Imhoff, Gonzalo Camacho tries; Nicolas Sanchez 2 conversions, 2 dropped goals, penalty, Felipe Contepomi penalty), Wales 12 (Leigh Halfpenny 4 penalties). HT: 6-9