Substitue Kyah Simon scored the winner for the Aussie’s, 10 minutes before the final whistle.
An injury kept her out of acyion for over a year and ruled her out of the Matildas runner-up finish in the Asian Cup and cast doubt over her career.
“When you watch the girls on TV at the Asian Cup and you know you should be there, it was pretty tough,
It was a tough road and I think I definitely came out of the other side mentally tougher.” said Simon.
The Matildas now head to the quarter-finals whre they will meet the winner of the tie between Netherlands and Japan.
Brazil were unbeaten in the tournament having won all three of their group stage matches, but could not create chances against a determined and focused Aussie defence.
This is the first time Australia has won in the knock-out stages of the World Cup.