Mathew Leckie's fantastic solo finish earned Australia a spot in the World Cup round of 16 for the first time since 2006.
Denmark came into this match knowing that they needed a win regardless of what occurred in the other Group D match between Tunisia and France, and Kasper Hjulmand’s men started on the front foot.
Despite pinning Australia back in their own third, the Danes were unable to truly test Matt Ryan, with their final ball lacking much quality.
Their best chance came in the 19th minute when the Australian keeper was forced to make a stop with his feet after Harry Souttar almost scored an own goal from a Joakim Maehle cross.
In the second half, both teams looked quite lethargic with the ball. It wasn’t until the news that Tunisia had scored against France made its way through that Australia finally started to look better in attack, and it only took a few minutes for Leckie to counter, twist away from Maehle, and get the ball past Kasper Schmeichel at the far post.
Denmark looked shell-shocked while the celebrations took part, and the team had little success in getting past the Australian backline after conceding.
Australia will next face the winners from Group C, which contains Argentina, Poland, Saudi Arabia and Mexico.