Martinsville is a city in Clark County, Illinois, United States. The population was 1,167 at the 2010 census.
Martinsville is located at 39°20′18″N 87°52′55″W (39.338369, -87.881940).
According to the 2010 census, Martinsville has a total area of 2.08 square miles (5.39 km2), of which 2.05 square miles (5.31 km2) (or 98.56%) is land and 0.03 square miles (0.08 km2) (or 1.44%) is water.
As of the census of 2000, there were 1,225 people, 522 households, and 358 families residing in the city. The population density was 596.0 people per square mile (229.6/km²). There were 593 housing units at an average density of 288.5 per square mile (111.1/km²). The racial makeup of the city was 99.35% White, 0.16% Native American, 0.08% Asian, 0.08% from other races, and 0.33% from two or more races. Hispanic or Latino of any race were 0.24% of the population.
There were 522 households out of which 31.0% had children under the age of 18 living with them, 54.2% were married couples living together, 9.2% had a female householder with no husband present, and 31.4% were non-families. 29.7% of all households were made up of individuals and 15.9% had someone living alone who was 65 years of age or older. The average household size was 2.35 and the average family size was 2.86.