Castro County is a county located in the U.S. state of Texas. As of the 2020 census, its population was 7,371. Its county seat is Dimmitt. The county was named for Henri Castro, who was consul general to France for the Republic of Texas and the founder of a colony in Texas. The county was created in 1876 and was organized in 1891. On April 10, 2023, an explosion and subsequent fire at South Fork Dairy, about 10 miles south of Dimmitt, resulted in the deaths of an estimated 18,000 dairy cattle.