Centralia is a city in Boone County, Missouri, United States. The population was 4,541 at the 2020 census, with an estimated population of 4,244 in 2018. A very small portion of the city lies in Audrain County.

The Boone County portion of Centralia (which forms the majority of the city) is part of the Columbia Metropolitan Statistical Area, while a small part in Audrain County is part of the Mexico Micropolitan Statistical Area.

According to the United States Census Bureau, the city has a total area of 2.84 square miles (7.36 km²), all land.

As of the 2020 census, Centralia had a population of 4,541. The median age was 37.0 years. 26.0% of residents were under the age of 18 and 17.7% of residents were 65 years of age or older. For every 100 females there were 89.3 males, and for every 100 females age 18 and over there were 84.9 males age 18 and over.

0.0% of residents lived in urban areas, while 100.0% lived in rural areas.

There were 1,808 households in Centralia, of which 35.2% had children under the age of 18 living in them. Of all households, 46.7% were married-couple households, 15.4% were households with a male householder and no spouse or partner present, and 30.3% were households with a female householder and no spouse or partner present. About 29.6% of all households were made up of individuals and 15.0% had someone living alone who was 65 years of age or older.

There were 1,930 housing units, of which 6.3% were vacant. The homeowner vacancy rate was 1.8% and the rental vacancy rate was 8.1%.

As of the census of 2010, there were 4,027 people, 1,601 households, and 1,063 families living in the city. The population density was 1,418.0 inhabitants per square mile (547.5/km²). There were 1,755 housing units at an average density of 618.0 units per square mile (238.6 units/km²). The racial makeup of the city was 96.5% White, 1.0% African American, 0.4% Native American, 0.2% Asian, 0.5% from other races, and 1.3% from two or more races. Hispanic or Latino of any race were 1.6% of the population.