The El Leoncito Astronomical Complex (Spanish: Complejo Astronómico El Leoncito - CASLEO) is an astronomical observatory in the San Juan Province of Argentina. CASLEO is one of two observatories located within El Leoncito National Park, which is in a part of the country which rarely sees cloud cover. The other facility in the park is the Carlos U. Cesco Astronomical Station of the Félix Aguilar Observatory. CASLEO was established in 1983 by an agreement between National Scientific and Technical Research Council (CONICET) of Argentina, the Ministry of Science, Technology and Innovation (MINCYT) of Argentina, the National University of San Juan (UNSJ), the National University of La Plata (UNLP), and the National University of Córdoba (UNC).