Grenville is a town in Day County, South Dakota, United States.

[6] Grenville was laid out in 1914, and named for the greenery of the original town site.

[7] According to the United States Census Bureau, the town has a total area of 0.24 square miles (0.62 km2), all land.

The racial makeup of the town was 95.16% White, 3.23% Native American, and 1.61% from two or more races.

There were no families and 30.0% of the population living below the poverty line, including no under eighteens and 54.5% of those over 64.