Lamar County is a county located in the U.S. state of Texas, in the Northeast Texas region. As of the 2020 census, its population was 50,088. Its county seat is Paris. The county was formed by the Congress of the Republic of Texas on December 17, 1840, and organized the next year. It is named for Mirabeau B. Lamar, the second president of the Republic of Texas. Lamar County comprises the Paris, TX micropolitan statistical area.