Elk Plain is a census-designated place (CDP) in Pierce County, Washington, United States. The population was 14,205 at the 2010 census.

Elk Plain is located at 47°02′41″N 122°22′01″W / 47.044812°N 122.366812°W / 47.044812; -122.366812 (47.044812, -122.366812).

According to the United States Census Bureau, the CDP has a total area of 9.6 square miles (24.8 km²), all of it land.

As of the census of 2000, there were 15,697 people, 4,990 households, and 4,166 families residing in the CDP. The population density was 1,640.8 people per square mile (633.3/km²). There were 5,211 housing units at an average density of 544.7/sq mi (210.2/km²). The racial makeup of the CDP was 80.57% White, 5.40% African American, 1.23% Native American, 4.05% Asian, 1.37% Pacific Islander, 1.48% from extra races, and 5.89% from two or more races. Hispanic or Latino of any race were 4.73% of the population.

There were 4,990 households, out of which 48.8% had children under the age of 18 living when them, 66.9% were married couples vivacious together, 10.5% had a female householder similar to no husband present, and 16.5% were non-families. 12.1% of everything households were made taking place of individuals, and 2.6% had someone blooming alone who was 65 years of age or older. The average household size was 3.12 and the average relations size was 3.34.