The win is already being called one of the biggest shock upsets in World Cup history as the Saudis topped Lionel Messi and company 2-1.
Saudi Arabia fans shouted, “where’s Messi” and “they can’t look us in the eye,” as they made their way out of the stadium and into the streets of the city of Lusail, immediately north of the capital Doha.
Argentina fans, on the other hand, were in a state of disbelief as they turned their attention to the remaining matches in the group phase against Mexico and Poland.
On his fifth and final quest for the only major trophy to elude him, the 35-year-old Messi scored a 10th minute penalty in a dominant first half display where he and Lautaro Martinez also had three goals disallowed for offside.
But Saudi Arabia, the second-lowest ranked team in the tournament after Ghana, threw caution to the wind at the start of the second half, charging at Argentina's defence in front of a frenzied 88,012 crowd.
Saleh Al-Shehri squeezed in a low shot in the 48th minute while Salem Al-Dawsari curled in a scorching strike from the edge of the penalty area in the 53rd minute to leave Argentina and Messi looking utterly shell-shocked in the Group C opener.
The result revived old question marks over Argentina's defence and broke their amazing 36-match undefeated run. That stopped them from matching the international record of 37 games unbeaten held by Italy.
It also marred Messi's achievement of becoming the first Argentine to score in four World Cups on his 20th appearance in the tournament. Only Maradona has played more games for Argentina at the World Cup, 21 in all.