Great Northern Highway is an Australian highway that links Western Australia's capital city Perth with its northernmost port, Wyndham. With a length of almost 3,200 kilometres (2,000 mi), it is the longest highway in Australia, with the majority included as part of the Perth Darwin National Highway. The highway, which travels through remote areas of the state, is constructed as a sealed, predominantly two-lane single carriageway, but with some single-lane bridges in the Kimberley. Economically, it provides vital access through the Wheatbelt and Mid West to the resource-rich regions of the Pilbara and Kimberley. In these areas, the key industries of mining, agriculture and pastoral stations, and tourism are all dependent on the highway.
In Perth, the highway begins in Midland near Great Eastern Highway, and further north intersects the Reid and Roe highways, which together form Perth's ring road. There are also three rural highways that spur off Great Northern Highway. Brand Highway and North West Coastal Highway provide an alternative coastal route between Muchea and Port Hedland, while Victoria Highway carries the National Highway route and interstate traffic into the Northern Territory. Various road routes are allocated to sections of Great Northern Highway, including the Highway 1 routes National Route 1 and National Highway 1, as well as National Highway 95. In 2024 the section north of Victoria Highway was assigned National Highway 1, as well as State Route 155
