Hooker County is a county in the U.S. state of Nebraska. As of the 2020 United States Census, the population was 711. Its county seat is Mullen, which is the county's only community of substantial size. In the Nebraska license plate system, Hooker County is represented by the prefix 93, because it had the smallest number of registered vehicles out of the state's 93 counties when the licensing system was established in 1922.