Lewisville (/ˈljuː.ɪs.vɪl/ LEW-iss-vil) is a city in Denton County, Texas, United States. It is a northwestern suburb of Dallas. The 2000 United States Census placed the city's population at 77,737 and the 2010 Census placed it at 95,290, making it one of the fastest-growing city populations in the United States and the 33rd most populous in Texas.