Elk Plain is a census-designated place (CDP) in Pierce County, Washington, United States.

[1] As of the 2020 census, there were 14,534 people, 4,967 households, and 3,821 families residing in the CDP.

There were 5,094 housing units at an average density of 607.9 per square mile (234.7/km2).

As of the 2010 census, there were 14,205 people, 4,707 households, and 3,759 families residing in the CDP.

There were 4,929 housing units at an average density of 641.0 per square mile (247.5/km2).

As of the 2000 census, there were 15,697 people, 4,990 households, and 4,166 families residing in the CDP.

12.1% of all households were made up of individuals, and 2.6% had someone living alone who was 65 years of age or older.