Road routes in New South Wales assist drivers navigating roads in urban, rural, and scenic areas of the state. Today all numbered routes in the state are allocated a letter (M, A, B or D) in addition to a one- or -two digit number, with 'M' routes denoting motorways, 'A' routes denoting routes of national significance, 'B' routes denoting routes of state significance, and 'D' for Detour routes of a major motorway. The route system includes the officially designated highways, urban and intercity motorways and arterial roads, and important cross-state roads that have not been declared highways.

Route numbers have been allocated to New South Wales' roads since 1954, with the introduction of National Routes across all states and territories in Australia, symbolised by a white shield with black writing; National Route 1 ('Highway 1') was one of the best-known numbered nation routes, likely due to its fame for circumnavigating the continent.

To supplement the National Route number system, three Ring Roads were introduced to Sydney in 1964, symbolised by a blue circular shield with white writing and a dotted outline.^[1] These lasted 10 years before their decommissioning in 1974.

In 1973 Freeway Routes were introduced to complement the state's National Routes and Sydney's Ring Roads, symbolised by blue rounded shields with white writing crowned by red crests as well, in an imitation of the American Interstate shield. Most of these routes were not signed as extensions opened, or were replaced with other routes in the years following, and while not officially decommissioned, virtually all signage of these routes were removed in 1992.

In 1974 the National Highway network was defined, which allowed some existing National Routes to be upgraded to National Highways. These were marked with the same shield design as the National Routes, except for their gold-on-green colouring and the word NATIONAL added across the top. The new State Routes system was also introduced in 1974, symbolised by blue rounded shields with white writing – much like the Freeway Routes, except without the red crests – and replaced Sydney's Ring Roads. Scores of other State Routes were designated across New South Wales, marking out urban arterial routes and secondary rural highways.

In 1992–1993 Sydney's Metroad system was introduced, symbolised by white hexagonal shields with blue writing, indicating Sydney's major radial and circumferential arteries. These routes subsumed many of the city's existing State Routes and also urban portions of National Routes and National Highways. A second, smaller allocation of Metroads were rolled out in 1998-9.

In 2013 the state replaced its entire system of National Routes, National Highways and Metroads with an alphanumeric route numbering system.^[2] Many existing numbered routes were allocated a letter (M, A, B or D) in addition to its number, with 'M' routes denoting motorways, 'A' routes denoting routes of national significance, 'B' routes denoting routes of state significance, and 'D' routes acting as motorway detours. Instead of shields, route numbers are displayed as yellow text on green rectangular backgrounds outlined in white, and has now – with the exception of Tourist Routes and a State Route or two – become the sole route numbering system in the state. The changeover to alphanumeric routes was announced in March 2013 and signs were updated between May and December 2013, either by removing old "shield" coverplates installed on newer signs, or installing new alphanumeric coverplates on old shielded signs,^[3] although some road projects (like Westlink M7 in 2005) or major highways (like Hume Highway from 1997) were allocated or converted to alphanumeric routes before the general change-over in 2013; these are noted. In 2020, the styling of the markers was modified to remove the white border, aligning with the design for all other states and territories except the ACT.^[4]

• Highways in Australia for highways in other states and territories
• Highways in New South Wales for details about officially gazetted highways
• List of road routes in the Australian Capital Territory
• List of road routes in the Northern Territory
• List of road routes in Queensland
• List of road routes in South Australia
• List of road routes in Tasmania
• List of road routes in Victoria
• List of road routes in Western Australia