Balhannah is a town in the Adelaide Hills about 30 km southeast of Adelaide, the capital of South Australia. It was established in 1839 as a farming community, and soon grew to incorporate two once adjoining towns: Gilleston (named for Osmond Gilles) and Blythetown.
It is on the main interstate railway between Adelaide and Melbourne. In the past it was the junction for a branch line that ran up the Onkaparinga Valley and beyond to Birdwood and Mount Pleasant.
Much of Balhannah is along Onkaparinga Valley Road, although there are some other residential streets, and Greenhill Road terminates near the town centre. One of the larger businesses in the town is a long-established hardware store, now part of the Mitre 10 chain. The fruit cold store built in 1914 was one of the first in Australia and is still in use.