Castalia is a city in Winneshiek County, Iowa, United States.

[5] According to the United States Census Bureau, the city has a total area of 0.58 square miles (1.50 km2), all land.

[6] As of the census of 2020,[8] there were 145 people, 78 households, and 49 families residing in the city.

There were 78 housing units at an average density of 135.0 per square mile (52.1/km2).

At the 2010 census there were 173 people in 82 households, including 49 families, in the city.

There were 84 housing units at an average density of 144.8 per square mile (55.9/km2).

At the 2000 census there were 175 people in 79 households, including 48 families, in the city.

There were 81 housing units at an average density of 112.5 per square mile (43.4/km2).

About 21.7% of families and 15.4% of the population were below the poverty line, including 22.2% of those under the age of eighteen and none of those sixty five or over.