Marienville is an unincorporated community and census-designated place (CDP) in Jenks Township, Forest County, Pennsylvania, United States. Its altitude is 1,735 feet (529 m), and it is located at 41°28′12″N 79°7′29″W / 41.47000°N 79.12472°W / 41.47000; -79.12472 (41.4702014, -79.1247623). Other names for the community have included "Marion", "Marion Centre", and "Marionville". Marienville is a major point on a well-known ATV trail. According to the 2010 census the population of Marienville was 3,137.
Marienville is the location of the SCI Forest state penitentiary.