Castana is a city in Monona County, Iowa, United States. The population was 178 at the 2000 census.
The city was founded in the summer of 1866 by A.G. Hammond, formerly a resident of Hartford, Connecticut. However Mr. Hammond died and a Mr. Day, who had been employed to work on the building, formed a company and completed building a store, which opened amid much celebration on 4 July 1867. Day then secured the office of post master and by 1872 there was also a blacksmith shop, two other shops and a franchise of Penn Bros, with a methodist minister living nearby and also a mill. Efforts to encourage the American Emigrant Company to provide funds of $2,000 to start a school lost out to a rival project in Belvidere.
Castana is located at 42°4′21″N 95°54′30″W / 42.0725°N 95.90833°W / 42.0725; -95.90833 (42.072518, -95.908266).