Dallas County is a county located in the U.S. state of Texas. As of the 2020 census, the population was 2,613,539, and was estimated to be 2,656,028 in 2024, making it the second-most populous county in Texas and the eighth-most populous county in the United States. Its county seat is Dallas, the third-most populous city in Texas and the ninth-most populous city in the United States. The county was founded on March 30, 1846 and was possibly named for George Mifflin Dallas, the 11th Vice President of the United States under U.S. President James K. Polk. Dallas County is included in the eleven-county Dallas–Fort Worth–Arlington metropolitan statistical area, which is the fourth-most populous metropolitan area in the United States.
Municipal expansion within Dallas County has blurred the geographic lines between cities and between neighboring counties.
