Iran became the second team to qualify for next year's World Cup finals with a 1-0 home victory over Bahrain on Wednesday that sparked frenzied celebrations.
Japan were the first country to claim a spot alongside 2006 hosts Germany with victory over North Korea earlier on Wednesday and Iran joined them after a confident performance.
Hundreds of thousands of fans poured on to the streets of the capital Tehran, setting off firecrackers, blowing whistles and waving national flags.
Groups of young men and women shouted praise for Iran as they leaned out of car windows blaring loud pop music.
Iran only needed a point to reach their third World Cup finals but defender Mohammad Nosrati gave them a psychological cushion with a firm header two minutes into the second half.
Mehdi Mahdavikia twice came close as the home side continued to dominate their Gulf rivals but Nosrati's effort proved to be enough.
The 70,000 crowd at Azadi Stadium erupted in delight at the final whistle as fireworks illuminated the night sky.
Scores of fans ran on to the pitch clutching flags before stewards regained control. One banner read "Long live Iran, Hello Germany".
DREAM GOAL
"I had a dream last night about scoring a goal," said match-winner Nosrati. "With God's help, we won. We played very well and deserved to win."
Iran previously qualified for the World Cup finals in 1978 and 1998.
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Iran's win over Bahrain sent them back to the top of Group B with 13 points from five games, one more than Japan.
Bahrain will finish third in Group B after North Korea's defeat and contest a two-leg playoff with the third-placed team in Group A.
The winner of that contest will play the fourth-placed team in the CONCACAF zone for a place at the World Cup finals. The top two from the two Asian group's qualify automatically.
Iran's final group game is away to Japan on August 17.
(Additional reporting by Parisa Hafezi)