Double dissolution is a mechanism under the Australian Constitution (section 57) that allows the Governor-General, on the advice of the Prime Minister, to dissolve both the House of Representatives and the entire Senate simultaneously - triggering a general election for all 150 lower house seats and all 76 Senate seats at once. Typically, at most federal elections, only half of the senate seats are up for elction.

It's a constitutional "pressure valve" designed to resolve a deadlock between the two chambers. If the government wins the election and the triggering bill is still blocked, it can convene a rare joint sitting of both houses to pass the legislation by absolute majority.

Because all Senate seats are contested at once, the quota to win a Senate seat is lower than normal - making it easier for minor parties and independents to get elected. This has historically increased crossbench complexity and the mechanism has rarely been used.