The Hartung–Boothroyd Observatory (HBO) is located atop Mount Pleasant near Cornell University outside of Ithaca, New York (US).

The observatory is named to recognize funding from M. John Hartung, a 1908 Cornell graduate and later chemical industrialist, and to honor Samuel L. Boothroyd, the founder of Cornell's Department of Astronomy.

The primary 0.6m mirror was constructed from a Pyrex 1/8-scale test pouring as part of technology development for the Palomar Observatory 200-inch telescope.

The mirror was polished and mounted in a lightweight tube in the late 1930s under Boothroyd's direction, but World War II deferred its planned use in a high-altitude observatory.

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