Washington County is a county located in the U.S. state of Mississippi. As of the 2020 census, the population was 44,922. Its county seat is Greenville. The county is named in honor of the first president of the United States, George Washington. It is located to the Arkansas border.

Greenville is the ninth-most populous city in the U.S. state of Mississippi, and the largest city by population in the Mississippi Delta region. It is the county seat of Washington County. The population was 29,670 at the 2020 Census.