South Australia

South Australia is the country's fifth most populous state, with roughly 1.85 million residents centred on Adelaide on the southern coast. The state runs from the Eyre Peninsula in the west across the Flinders Ranges and the Murray mouth to the Coorong, and its economy is anchored by viticulture in the Barossa and Clare Valleys, agriculture in the cereal-growing south-east, defence manufacturing at Osborne, and mining in the Far North at sites like Olympic Dam. Adelaide is also a long-standing centre for festivals and the arts, hosting WOMADelaide and the Adelaide Festival each summer.

Plates issued in South Australia follow the S123-ABC format: a leading letter S, three digits, then three letters, e.g. S123-ABC. The current series is administered by the Department for Infrastructure and Transport on a white base with black characters and "South Australia" set across the top as a wordmark. The leading S is the most distinctive feature of South Australian plates and serves as an at-a-glance identifier: no other Australian state or territory issues passenger plates starting with that letter, so a plate beginning with S is almost always SA-registered. The S prefix was introduced in the early 2000s after the older general-issue series approached its combinatorial limit.

South Australian plate strings do not encode the registration suburb or region. A plate first issued in Mount Gambier reads identically, in form, to one issued in metropolitan Adelaide or in Whyalla. Personalised plates (administered through SA Plates) and heritage-themed combinations sit alongside the standard series with their own conventions and are out of scope for the standard validator. Heavy vehicles, trailers, and motorcycles each carry their own parallel sequence. On an SA road today, the standard S123-ABC shape dominates the passenger fleet.