List of road routes in South Australia

[3] Former National Highways still retained their shield design (including NATIONAL markings) after conversion, but were modified in 2017 to remove them, bringing their design in line with the rest of the state.

All alphanumeric routes listed here are derived from the Government of South Australia's Location SA service.

[4] Roads allocated an M route are usually at least dual-carriageway motorways or expressways, with at least two lanes in each direction.

They highlighted the interstate links connecting major population, industrial and principal regions of New South Wales to the rest of the Australia, in a way that was readily identifiable to interstate travellers.

Like National Routes, South Australia's National Highways were also replaced with the alphanumeric system, introduced across the state in 1998: each route was converted to an alphanumeric route number, all keeping their number during the conversion, but also initially keeping the National green-and-gold shield design; this was eventually eliminated in 2017.

South Australia never adopted State Routes, but allowed two Victorian rural State Routes to cross the border and terminate in South Australian locations within 20 km of it when they were rolled out there in 1985; these were replaced by their Victorian equivalent alphanumeric allocations in 1998.