Pinnaroo is a town in the Murray Mallee region of South Australia, near the border with Victoria, 243 km east of Adelaide. Pinnaroo is on the Mallee Highway, and on the railway line between Tailem Bend and Ouyen. The roadhouses on the highway at Pinnaroo are the first food and leg-stretch stop on the bus route from Adelaide to Sydney. At the 2006 census, Pinnaroo had a population of 558.
The town's name is derived from a word for "big man" in a local Aboriginal language.
The railway arrived in the area in 1906. There had not been any significant development in the area before that, as the remoteness and difficulty of getting supplies in and produce out had made it uneconomic to farm before that.
The railway is not currently available for transport between the states, as the line from Tailem Bend was converted to standard gauge soon after the main Adelaide–Melbourne line was converted, but the line to Ouyen remains as broad gauge. Both sides are used to transport grain from silos along the railway line towards the ports in each state.
The town has a large variety of sports, such as Australian rules football, netball, cricket, tennis, basketball, volleyball, lawn bowls, badminton, golf and darts. The local football team, the Pinnaroo Supa Roos play in the Mallee Football League.
The town has become a major centre for growing potatoes since around 1990. Pinnaroo hosts the 'Pinnaroo SpudFest' each year. The SpudFest features a black tie dinner, stalls and games, entertainment, and 'spud wrestling'.