Rockwall County is a county in the U.S. state of Texas. As of the 2020 census, its population was 107,819; it was estimated to be 140,738 in 2025. Its county seat is Rockwall and both the county and city are named for a wall-like subterranean rock formation that runs throughout the county. Rockwall County is part of the Dallas–Fort Worth–Arlington metropolitan statistical area. It was one of the 25 fastest-growing counties in the U.S. in 2009. Rockwall County is listed as the wealthiest county in Texas and the 17th-wealthiest in the United States by median household income. Cities in Rockwall County include Rockwall, Heath, Royse City, Fate, McClendon-Chisholm, Mobile City, and part of Rowlett.