Australia's Highway 1 is a network of highways that circumnavigate the country, joining all mainland capital cities except the national capital of Canberra. At a total length of approximately 14,500 km (9,000 mi) it is the longest national highway in the world, surpassing the Trans-Siberian Highway and the Trans-Canada Highway. Over a million people traverse some part of the highway network every day. It is the longest continuing highway in the world as the Pan-American Highway is separated by the Darién Gap and AH1 is separated by the Sea of Japan.

Highways in Australia are generally high capacity roads managed by state and territory government agencies, though Australia's federal government contributes funding for important links between capital cities and major regional centres. Prior to European settlement, the earliest needs for trade and travel were met by narrow bush tracks, used by tribes of Indigenous Australians. The formal construction of roads began in 1788, after the founding of the colony of New South Wales, and a network of three major roads across the colony emerged by the 1820s. Similar road networks were established in the other colonies of Australia. Road construction programs in the early 19th century were generally underfunded, as they were dependent on government budgets, loans, and tolls; while there was a huge increase in road usage, due to the Australian gold rushes. Local government authorities, often known as Road Boards, were therefore established to be primarily responsible for funding and undertaking road construction and maintenance. The early 1900s saw both the increasingly widespread use of motorised transportation, and the creation of state road authorities in each state, between 1913 and 1926. These authorities managed each state's road network, with the main arterial roads controlled and maintained by the state, and other roads remaining the responsibility of local governments. The federal government became involved in road funding in the 1920s, distributing funding to the states. The depression of the 1930s slowed the funding and development of the major road network until the onset on World War II. Supply roads leading to the north of the country were considered vital, resulting in the construction of Barkly, Stuart, and Eyre Highways.