Viola (pronounced vy-OLA) is a village in Mercer County, Illinois, United States. The population was 955 at the 2010 census, a decline of one person from 956 in 2000.
According to the 2010 census, Viola has a total area of 0.855 square miles (2.21 km2), of which 0.84 square miles (2.18 km2) (or 98.25%) is land and 0.015 square miles (0.04 km2) (or 1.75%) is water.
As of the census of 2000, there were 956 people, 383 households, and 274 families residing in the village. The population density was 1,155.8 people per square mile (444.7/km2). There were 401 housing units at an average density of 484.8 per square mile (186.5/km2). The racial makeup of the village was 98.22% White, 0.84% from other races, and 0.94% from two or more races. Hispanic or Latino of any race were 1.78% of the population.
There were 383 households, out of which 32.6% had children under the age of 18 living with them, 60.1% were married couples living together, 8.9% had a female householder with no husband present, and 28.2% were non-families. 26.1% of all households were made up of individuals, and 13.1% had someone living alone who was 65 years of age or older. The average household size was 2.50 and the average family size was 3.03.