Castlemaine is a small city in Victoria, Australia, in the goldfields region of Victoria about 120 kilometres northwest by road from Melbourne and about 40 kilometres from the major provincial centre of Bendigo. It is the administrative and economic centre of the Shire of Mount Alexander. The population at the 2011 Census was 6,751.
It was named by the chief goldfield commissioner, Captain W. Wright, in honour of his Irish uncle, Viscount Castlemaine.
It is home to many cultural institutions including the Theatre Royal, the oldest continuously operating theatre in mainland Australia.