Opelousas is a small city and the parish seat of St. Landry Parish, Louisiana, United States. Interstate 49 and U.S. Route 190 were constructed with a junction here. According to the 2020 census, Opelousas has a population of 15,786, a 6.53 percent decline since the 2010 census, which had recorded a population of 16,634. Opelousas is the principal city for the Opelousas-Eunice Micropolitan Statistical Area, which had an estimated population of 80,808 in 2020.