After defeating Peru on penalties in an intercontinental play-off in Qatar, Australia became the 31st side to qualify for the 2022 World Cup.
Alex Valera's final attempt was saved by goalkeeper Andrew Redmayne, who replaced Mat Ryan moments before the shootout for his third cap.
Australia has qualified for every World Cup since 2006, and this will be their fifth in a row.
They'll be in Group D with France, Denmark, and Tunisia, the current holders.
Costa Rica will meet New Zealand at the Ahmad bin Ali Stadium on Tuesday to determine the World Cup's final team.
'It was a gamble, but it paid off,' Arnold says of Redmayne's replacement.
Graham Arnold's decision to replace captain Ryan with Redmayne, who has never played for Australia before, was a bold one. It was surprise that the competitive international was against Nepal, but it paid out in the end.
The 33-year-old Sydney FC goalkeeper danced on the line for each kick in an attempt to frighten the Peruvians, and Luis Advincula's penalty was saved before Valera's last penalty was saved.
"He's a great penalty saver, and I did something that may have a mental impact on them," Arnold explained.
"I'm sure they were thinking to themselves, 'Why is this person being brought on, he had to be excellent.'
"Perhaps that's why they struck the post." It takes a 1% mental effort to annoy Peru's penalty takers. It was a gamble, but it paid off."
Redmayne was making his third appearance for the Socceroos, having had tryouts with Arsenal as a kid.
"This concept was floated pre-selection that this may happen in these kinds of conditions, and I've kind of had that in my mind for the two or three weeks we've been here [in Qatar]," Redmayne added.
"In training, I've been working on a few things, but at the end of the day, it's a coin flip, right or left." "I'm not a hero; I just performed my job tonight like everyone else."
In Al Rayyan, the game itself was far from a classic, with no notable chances in the first 80 minutes. In the closing ten minutes, Australia had three decent chances, with Ajdin Hrustic forcing two saves and Aziz Behich curling narrowly wide.
Peru's sole attempt on target came in extra time, but Edison Flores' long-range strike flew straight at Ryan. When his header hit the post, he came even closer to scoring the game's finest goal.