Seneca is a town in Faulk County, South Dakota, United States.

[7] According to the United States Census Bureau, the town has a total area of 0.42 square miles (1.09 km2), all land.

There were 29 housing units at an average density of 69.0 per square mile (26.6/km2).

31.3% of all households were made up of individuals, and 18.8% had someone living alone who was 65 years of age or older.

There were 36 housing units at an average density of 87.5 per square mile (33.8/km2).

46.4% of all households were made up of individuals, and 25.0% had someone living alone who was 65 years of age or older.

There were 25.0% of families and 20.0% of the population living below the poverty line, including no under eighteens and 16.0% of those over 64.