Doña Ana County is a county located in the southern part of the New Mexico, United States. As of the 2020 U.S. Census, its population was 219,561, which makes it the second-most populated county in New Mexico. Its county seat is Las Cruces, the second-most populous municipality in New Mexico after Albuquerque, with 111,385 as of the 2020 U.S. Census. The county is named for Doña Ana Robledo, who died there in 1680 while fleeing the Pueblo Revolt.