Leoncito Astronomical Complex, Astronomical observatory in El Leoncito National Park, Argentina.

The Leoncito Astronomical Complex is a research facility located inside El Leoncito National Park in San Juan Province, sitting at 2552 meters above sea level. It houses several telescopes, including the Jorge Sahade telescope, which has a mirror measuring 2.15 meters across.

The idea of a large Argentine telescope dates to the mid-1940s, and Jorge Sahade settled on a 2.15 m instrument after consulting experts in the United States. The complex was formally created on 10 May 1983 by CONICET, SUBCYT and the universities of La Plata, Córdoba and San Juan, and inaugurated on 12 September 1986. Regular observations began on 1 March 1987. The donated estancia had hosted Yale astronomers in the early 1960s.

The complex is named after the El Leoncito ranch, whose owner Héctor Hilario Zamarbide gave Yale scientists access in the early 1960s. The 2.15 m telescope is named for Jorge Sahade, who proposed its size after consulting experts in the United States. The Helen Sawyer Hogg telescope, dedicated to the Canadian astronomer, was moved here from Chile in 1998.

Researchers who want to use the telescopes need to submit a proposal to an access committee, while general visitors can join guided tours of the site. Tours run during the day and in the evening, offering a look at the instruments and how the facility works.

The site records more than 250 cloudless nights per year, which is rare even among high-altitude observatories in South America. The telescopes can also be operated remotely, so scientists at other institutions can run observations without traveling to the site.