A stunning strike from Salem Al Dawasari completed a shock turnaround for Saudi Arabia at the Lusail Iconic Stadium, as they upset well-fancied tournament favourites Argentina in their group opener.
Lionel Messi opened the scoring from the penalty spot for La Albiceleste after just 10 minutes, after Leandro Paredes was brought down.
However, that seemed a distant memory by the hour mark, after Saleh Al Shehri levelled the scores by firing across Emi Martinez, all before Al Dawasari fired the Green Falcons in front with a sublime effort.
In Argentina's first loss in three years, it was definitely not the start Messi and Argentina wanted in his last international tournament.
The pressure cooker that is the Argentinian national team will only be feeling the heat even more now, as they look ahead to Saturday, when they face Mexico.
As for Herve Renard and Saudi Arabia, it is the dream start. Winning just once against Egypt in Russia four years ago, their showing in Lusail will be without doubt their most notable international result.
Story of the match
Messi should have opened the scoring after just two minutes in Lusail.
The ball fell kindly to him in the area after Angel Di Maria drove down the right-hand side, but his effort towards goal was smartly stopped by Mohammed Al Owais.
But it was not long before Argentina's captain could make amends.
After Saud Abdulhammid brought down Paredes in the box, Messi coolly slotted the ball into the bottom-left corner from 12 yards to give La Selección an early lead.
Messi and Lautaro Martinez could have both been on a brace just after 30 minutes.
Messi's cool finish and two sublime finishes from Martinez were all ruled out by the offside flag as the Green Falcons were doing all they could to stay in the game.
Just moments after the break, though, Saudi Arabia drew level.
Firas Al-Buraikan lofted the ball forwards for Al-Shehri, who fired the ball across Martinez and into the bottom right to level the scores.
And the Saudis would be in dreamland minutes later.
Allowed to bring the ball down in the area, Al Dawasari worked an angle for a shot with some clever footwork, all before firing the ball into the top right corner.
Argentina were unlucky not to break back, after a bouncing ball was inadvertently aimed towards goal by substitute Lisandro Martinez, only for Al Owais to make the save low to his right.
In stoppage time, a loose ball from Rodrigo De Paul's delivery was fired towards goal by substitute Julian Alvarez with goalkeeper Al Owais on the floor but the Saudi defence headed the ball off the line.
La Albiceleste huffed and puffed at the Green Falcons' defence, but the 11 men of Saudi Arabia stood firm in the face of Messi and Co. to claim the most shocking of opening round victories in Qatar.
Player of the match
Mohammed Al Owais
Despite the efforts of Al Shehri and Al Dawasari, it was the Saudi goalkeeper Al Owais who impressed most.
Had it not been for the early penalty, he may well have kept a clean sheet here against Argentina's star-studded front line.
However, as per WhoScored, he still made four saves in the match and scored a match rating of 7.6, making the defensive difference for the Green Falcons in Lusail.
Lineups
Argentina XI: Martinez (GK), Molina, Romero, Otamendi, Tagliafico, De Paul, Paredes, Di Maria, Messi (C), Papu Gomez, Martinez
Saudi Arabia XI: Al-Owais (GK), Al Shahrani, Al Boleahi, Tambakati, Abdulhamid, Al Dawasri, Al Malki, Kanno, Al Shehri, Al Faraj (C) (Bahrebi 45'), Al Buraikan