In Saudi Arabia, King Salman announced a snap public holiday for all workers and students in the kingdom in celebration of the win.
People watching the match at a fan zone in the capital, Riyadh, jumped with joy and cheered as the game ended. Drivers honked their horns in celebration. Saudi authorities also allowed free entry to a state-sponsored sports and entertainment festival.
The gravity of the victory will eventually sink in. Saudi Arabia is a team that had only ever won three World Cup matches in its history prior to Tuesday's game.
"One for the books," Saudi Arabia coach Herve Renard said. "Sometimes things are completely crazy."
Renard has has also coached Angola and Morocco, which he guided to the 2018 World Cup in Russia. He took over Saudi Arabia in 2019.
"We made history for Saudi football," Renard said. "It will stay forever. This is the most important. But we also need to think about looking forward because we still have two games that are very very difficult for us."
Renard said he asked his players to limit the celebration after the game to 20 minutes.
"That's all," he said. "But there are still two games - or more."
They still must face Poland on Saturday and then take on Mexico next Tuesday in Group C. Both are probably still favorites against Saudi Arabia - despite the upset.
He also suggested another possible truth: Messi and Argentina probably underestimated Saudi Arabia, which is only No. 51 in the FIFA ranking. Argentina is No. 3.
"But you know the motivation is not like you are playing Brazil," he added.