Waller County is a county in the U.S. state of Texas. As of the 2020 census, its population was 56,794. Its county seat is Hempstead. The county was named for Edwin Waller, a signer of the Texas Declaration of Independence and first mayor of Austin. Waller County is included in the Houston-The Woodlands-Sugar Land, TX metropolitan statistical area. It is home of the Prairie View A&M University.