The Fulton Opera House, also known as the Fulton Theatre or simply The Fulton, is a League of Regional Theatres class B regional theater located in historic downtown Lancaster, Pennsylvania. It is reportedly the oldest working theatre in the United States. It was designated a National Historic Landmark in 1964.

Lancaster is a city in and the county seat of Lancaster County, Pennsylvania, and one of the oldest inland cities in the United States. With a population of 58,039 at the 2020 census, it is the tenth-most-populous city in the state. The Lancaster metropolitan area population is 552,984, making it the second largest in the South Central Pennsylvania area.