Dimmitt is a city in Castro County, Texas, United States. The population was 4,375 at the 2000 census. It is the county seat of Castro County. It is located on the old Ozark Trail, a road system from St. Louis, Missouri, to El Paso, Texas. The Ozark Trail is marked at the courthouse.
Dimmitt is located at 34°32′57″N 102°18′55″W / 34.54917°N 102.31528°W / 34.54917; -102.31528 (34.549052, -102.315355).
According to the United States Census Bureau, the city has a total area of 2.1 square miles (5.4 km²), all of it land. Dimmitt is south of Hereford, the seat of Deaf Smith County.