Cerro Armazones is a mountain located in the Sierra Vicuña Mackenna of the Chilean Coast Range of Andes, approximately south-east of Antofagasta in the Antofagasta Region, Chile. The mountain is located in a privileged zone for optical astronomy because it has 89% cloudless nights a year. On 26 April 2010, the European Southern Observatory Council selected Cerro Armazones as the site for the planned Extremely Large Telescope (ELT); the construction began in June 2014, and the first light is expected in 2027. Before the construction of the ELT began, the elevation of Cerro Armazones had been , but now the top is truncated and the resulting plateau is several meters lower.
On the neighbouring hill, to the southwest and below Cerro Armazones, there is the Polish astrophysical observatory, the Cerro Armazones Observatory, managed by the Nicolaus Copernicus Astronomical Center of the Polish Academy of Sciences in Warsaw; observations are conducted by the Araucaria Project.