Apache Point Observatory, Astronomical observatory in Sunspot, New Mexico, United States.

Apache Point Observatory is an astronomical research facility in the Sacramento Mountains at Sunspot, New Mexico, about 18 miles south of Cloudcroft. Its telescopes stand under separate enclosures: the ARC 3.5 m Ritchey-Chrétien reflector on an alt-azimuth mount, the SDSS 2.5 m reflector with a 3° field of view under a roll-off roof, the NMSU 1.0 m reflector, and the 0.5 m ARCSAT on an equatorial mount.

The Astrophysical Research Consortium was formed in 1984 by five institutions, including New Mexico State University, to build a 3.5 m telescope. Construction of its building began in 1985, but full operations were delayed until November 1994 by problems fabricating the primary mirror; from 1991 to early 1993 a 1.8 m mirror was fitted instead. The SDSS 2.5 m telescope began operating in 2000.

The observatory's name comes from its site near Apache Point in the Sacramento Mountains, and its address is 2001 Apache Point Road, Sunspot. The 2.5 m telescope was built for the Sloan Digital Sky Survey, which by 2004 had led to the discovery of 541 asteroids with permanent designations. The 3.5 m telescope carries the APOLLO laser, which has measured the Earth-Moon distance since October 2005.

Access to the telescopes and buildings is private and restricted, so the site cannot be visited on a self-guided basis. The observatory stands in the Sacramento Mountains at Sunspot, about 18 miles (29 km) south of Cloudcroft, and the address is 2001 Apache Point Road. Observers on the 3.5 m telescope can work remotely through the Telescope User Interface (TUI) over the internet.

The observatory houses a specialized laser system that measures Earth-Moon distances with millimeter-level precision. This system provides data for gravity research and helps scientists understand celestial mechanics.