Pre-tournament favourites Argentina endured the worst possible start to their World Cup campaign as their 36-game unbeaten run came to an end with a deserved 2-1 defeat to Saudi Arabia.
Lionel Messi scored a penalty inside ten minutes but a fight-back from Saudi Arabia was sealed with excellent goals from Saleh Al-Shehri and Salem Al-Dawsari after the break.
Messi's first sight of goal came inside two minutes as he ran on to a loose ball but just couldn't bend his effort away from Saudi stopper Mohammed Al Owais.
Their fast start continues as VAR chimed in to award Argentina a penalty in the eighth minute as Saud Abdulhamid was seen pulling Leandro Paredes' shirt, and up stepped Messi to open the scoring with a composed finish from 12 yards.
Saudi Arabia responded well, however, with their high press causing plenty of problems for Argentina as Lionel Scaloni's men retained possession but didn't always look comfortable doing so.
The Saudi high line created plenty of space in behind and Messi looked to have exploited that when he finished off a one-on-one 22 minutes in, only for the offside flag to correctly rule it out. Lautaro Martinez had the ball in the back of the net twice in the next ten minutes but both efforts met the same fate.
Despite Argentina having the ball in the back of the net four times in the first half, they were only 1-0 up at the break, with Saudi Arabia still very much in the game.
That profligacy was punished as Saleh Al-Shehri beat Cristian Romero for pace and arrowed a great strike across the goal and into the bottom corner.
Eight minutes into the second half, Argentina were behind as Salem Al-Dawsari curled a glorious effort from the edge of the penalty area into the top corner. A truly sensational strike.
A sensational challenge from Hassan Altambakti prevented Messi from tapping home an equaliser, before Nicolas Tagliafico failed to convert from around two yards as Al Owais pulled off a superb save to keep his side ahead.
Argentina's search for a second goal came through constant crosses into the box but they rarely posed any real threat, aside from a soft Messi header which was gleefully collected by the goalkeeper.
Julian Alvarez saw an effort hooked away off the line in stoppage time as Argentina desperately tried to claw their way back into the game, but they just couldn't find another way through the sensational Saudi defence.
The game ended on a sour note as Yasir Al Shahrani was caught by the knee of his goalkeeper in a desperate attempt to clear the ball. The left-back was moving before being stretchered off and was seen giving the thumbs up, determined not to let his condition spoil a momentous victory for Saudi Arabia.
Argentina vs Saudi Arabia player ratings
1. Argentina (4-4-2)
GK: Emiliano Martinez - 6/10 - Didn't have much to do at all aside from picking the ball out of his net.
RB: Nahuel Molina - 5/10 - Didn't offer enough going forward and faded at the back.
CB: Cristian Romero - 5/10 - Got brutally nutmegged in the first half and beaten for the goal. Didn't look fully fit.
CB: Nicolas Otamendi - 6/10 - Had a tough battle against the Saudi forwards and largely did alright.
LB: Nicolas Tagliafico - 6/10 - Most of Saudi Arabia's early threat came down Tagliafico's side and the left-back did very well to deal with it.
RM: Angel Di Maria - 4/10 - Felt wasted out wide. In a lot of space but not always involved in the game.
CM: Leandro Paredes - 4/10 - Didn't do enough and was caught out for the equaliser.
CM: Rodrigo de Paul - 3/10 - Not involved enough and guilty of unforced errors which invited pressure.
LM: Alejandro Gomez - 3/10 - Really struggled to impact the game from out wide. Not his strongest showing.
ST: Lionel Messi - 6/10 - A threat to the Saudi defence from the first minute, although he found space hard to come by in the second half.
ST: Lautaro Martinez - 4/10 - Some dangerous attacking runs but needs to revise the offside rule before the next game.
SUB: Julian Alvarez (59' for Gomez) - 5/10 - Didn't offer a whole lot down the left.
SUB: Enzo Fernandez (59' for Paredes) - 6/10 - Restored a bit of control to the midfield battle.
SUB: Lisandro Martinez (59' for Romero) - 6/10 - Didn't have much to do as all the action was at the other end of the pitch.
SUB: Marcos Acuna (70' for Tagliafico) - 5/10 - High crosses towards Martinzez and Messi didn't make much sense.
Manager: Lionel Scaloni - 4/10 - Couldn't adjust to the Saudi high line and his triple substitution on the hour mark didn't change much.
2. Saudi Arabia (4-1-4-1)
GK: Mohammed Al Owais - 8/10 - Benefitted from a number of offside calls but usually did his job when required. A great save from Tagliafico.
RB: Saud Abdulhamid - 7/10 - A really foolish decision to concede the penalty which marred an otherwise superb performance.
CB: Hassan Altambakti - 9/10 - Some really intelligent positioning to continuously catch Argentina offside. Made an unreal challenge to stop Messi early in the second half. Celebrated every tackle like a goal.
CB: Ali Al-Bulayhi - 8/10 - Similarly, made some brave decisions that regularly paid off.
LB: Yasir Al Shahrani - 7/10 - Really impressive down the left. Caught Di Maria out on a number of occasions.
DM: Abdulelah Al Malki - 7/10 - Probably a little too aggressive with his challenges but can't argue with the efficiency.
RM: Saleh Al-Shehri - 7/10 - Took his goal incredibly well and was a real pest for Argentina.
CM: Mohamed Kanno - 8/10 - All over the pitch as he dominated the midfield battle at both ends of the field. Really impressive.
CM: Salman Al-Faraj - 6/10 - Picked up an injury early on and battled on with it until just before half-time.
LM: Salem Al-Dawsari - 7/10 - An utterly sensational goal. They don't come much better on a stage like this.
ST: Firas Al-Buraikan - 7/10 - A rather fortunate assist for the first goal but it was no less than his play deserved.
SUB: Nawaf Al-Abid (45' for Al-Faraj) - 6/10 - Brought some nice energy in midfield.
SUB: Sultan Al Ghanam (78' for Al-Shehri) - 6/10 - Did his job to help out at the back.
SUB: Abdulelah Al Amri (88' for Al-Abid) - N/A
SUB: Haitham Asiri (88' for Al-Buraikan) - N/A
SUB: Mohammed Al Burayk (99' for Al Shahrani) - N/A
Manager: Herve Renard - 9/10 - A really bold strategy which saw his side allow three offside goals in the first half, but you can't argue with the results. Renard took a massive risk and it paid off.