Bryn Athyn is an affluent home rule municipality in Montgomery County, Pennsylvania, United States. It was formerly a borough, and its official name remains "Borough of Bryn Athyn". The population was 1,375 at the 2010 census. It was formed for religious reasons from Moreland Township on February 8, 1916. Bryn Athyn is surrounded by Lower Moreland Township. "Bryn Athyn" was intended to mean "Hill of Unity" by its founders. "Bryn" is Welsh for "hill"; the source of "athyn" is unclear.