The Manastash Ridge Observatory (MRO) is an astronomical observatory built in 1972 by the University of Washington. It is located in a remote area approximately 14 kilometers (8.7 mi) west of Ellensburg, Washington, and can be reached by dirt roads from Ellensburg or Selah. The observatory features a 0.75 m (30 in) Ritchey-Chrétien telescope built by Boller and Chivens.