Williamsville is a city in Wayne County, Missouri, United States, along the Black River.

[5] According to the United States Census Bureau, the city has a total area of 0.32 square miles (0.83 km2), all land.

There were 188 housing units at an average density of 587.5 per square mile (226.8/km2).

29.7% of all households were made up of individuals, and 15.5% had someone living alone who was 65 years of age or older.

There were 190 housing units at an average density of 615.7 per square mile (237.7/km2).

30.4% of all households were made up of individuals, and 19.9% had someone living alone who was 65 years of age or older.