Steward Observatory is the research arm of the Department of Astronomy at the University of Arizona (UArizona). Its offices are located on the UArizona campus in Tucson, Arizona (US). Established in 1916, the first telescope and building were formally dedicated on April 23, 1923. It now operates, or is a partner in telescopes at five mountain-top locations in Arizona, one in New Mexico, one in Hawaii, and one in Chile. It has provided instruments for three different space telescopes and numerous terrestrial ones. Steward also has one of the few facilities in the world that can cast and figure the very large primary mirrors used in telescopes built in the early 21st century.

The Giant Magellan Telescope is a 25.4-meter, ground-based, extremely large telescope under construction at Las Campanas Observatory in Chile's Atacama Desert. Commissioning is anticipated in the early 2030s. Once complete, the Giant Magellan will be the largest Gregorian telescope ever built observing in optical and mid-infrared light. The telescope uses seven of the world’s largest mirrors to form a light collecting area of 368 square meters.