The Harvard College Observatory (HCO) is an institution managing a complex of buildings and multiple instruments used for astronomical research by the Harvard University Department of Astronomy. It is located in Cambridge, Massachusetts, United States, and was founded in 1839. With the Smithsonian Astrophysical Observatory, it forms part of the Center for Astrophysics | Harvard & Smithsonian.

The Smithsonian Astrophysical Observatory (SAO) is a research institute of the Smithsonian Institution, concentrating on astrophysical studies including galactic and extragalactic astronomy, cosmology, solar, earth and planetary sciences, theory and instrumentation, using observations at wavelengths from the highest energy gamma rays to the radio, along with gravitational waves. Established in Washington, D.C., in 1890, the SAO moved its headquarters in 1955 to Cambridge, Massachusetts, where its research is a collaboration with the Harvard College Observatory (HCO) and the Harvard University Department of Astronomy. In 1973, the Smithsonian and Harvard formalized the collaboration as the Center for Astrophysics | Harvard & Smithsonian (CfA) under a single Director.