Port Augusta (Goordnada in the revived indigenous Barngarla language) is a coastal city in South Australia about 310 kilometres (190 mi) by road from the state capital, Adelaide. Most of the city is on the eastern shores of Spencer Gulf, immediately south of the gulf's head, comprising the city's centre and surrounding suburbs, Stirling North, and seaside homes at Commissariat Point, Blanche Harbor and Miranda. The suburb of Port Augusta West is on the western side of the gulf on the Eyre Peninsula. Together, these localities had a population of 13,515 people in the 2021 census.

Formerly a seaport, the city supports regional agriculture and services many mines in the South Australian interior to its north. A significant industry was electricity generation until 2019, when its coal-burning power stations were shut down. A solar farm opened in 2020.

Port Augusta is part of Aboriginal Australians' Nukunu country, in which the local language is Barngarla. The last speaker of the language died in 1964, but successful efforts have been made to revive it based on a 3500-word dictionary compiled in the 1840s by German Lutheran pastor Clamor Wilhelm Schürmann. Its original Barngarla name is Goordnada.

It is a natural harbour, which was proclaimed on 24 May 1852 by Alexander Elder (brother of Thomas Elder) and John Grainger, having discovered it while aboard the Government schooner Yatala, captained by Edward Dowsett. The port was named after Augusta Sophia, Lady Young, the wife of the Governor of South Australia, Sir Henry Edward Fox Young. Lady Young was the daughter of Charles Marryat Snr., who had been a slaveholder in the British West Indies. Her brother was the Anglican minister Dean of Adelaide Charles Marryat.

Marine species include resident species and migrating visitors. Occasional sightings are made of whales, sunfish, swordfish and turtles.

The city and its surrounds had a population of 13,515 people in the 2021 census. It was therefore the fourth largest urban area outside of Adelaide after Mount Gambier, Whyalla and Port Lincoln. 83.4% of residents were born in Australia and 20.8% were Aboriginal or Torres Strait Islander. The most prevalent employment was community and personal service workers (17.7%), professionals (14.9%), technicians and trades workers (14.0%), labourers (13.1%), clerical and administrative workers (11.1%), sales workers (9.3%), machinery operators and drivers (9.3%), and managers (8.3%). The unemployment rate was 6.5% (South Australia: 5.4%). The median weekly household income was A$1277 per week.

Port Augusta is at the head of Spencer Gulf, a natural barrier to land transport, leading to the city being considered to be the "crossroads of Australia", the junction of major road and rail links.

Port Augusta is located at the eastern end of the Eyre Highway to Perth and at the northern end of the Augusta Highway to Adelaide. It is situated at the southern end of the Stuart Highway to Darwin. Virtually all road traffic across southern Australia passes through Port Augusta across the top of Spencer Gulf.