The Vera C. Rubin Observatory, formerly the Large Synoptic Survey Telescope (LSST), is an astronomical observatory in Coquimbo Region, Chile. Its main task is to conduct an astronomical survey of the southern sky every few nights, creating a ten-year time-lapse record, termed the Legacy Survey of Space and Time (also abbreviated LSST). The observatory is located on the El Peñón peak of Cerro Pachón, a 2,682-meter-high (8,799 ft) mountain in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes. The base facility is located about 100 kilometres (62 miles) away from the observatory by road, in La Serena.

The observatory is named for Vera Rubin, an American astronomer who pioneered discoveries about galactic rotation rates. It is a joint initiative of the U.S. National Science Foundation (NSF) and the U.S. Department of Energy's (DOE) Office of Science and is operated jointly by NSF NOIRLab and SLAC National Accelerator Laboratory.

The Rubin Observatory houses the Simonyi Survey Telescope, a wide-field reflecting telescope with an 8.4-meter primary mirror. The telescope uses a variant of three-mirror anastigmat, which allows the telescope to deliver sharp images over a 3.5-degree-diameter field of view. Images are recorded by a 3.2-gigapixel charge-coupled device imaging (CCD) camera, the largest camera yet constructed.

The Rubin Observatory was proposed in 2001 as the LSST. Construction of the mirror began (with private funds) in 2007. The LSST then became the top-ranked large ground-based project in the 2010 Astrophysics Decadal Survey, and officially began construction on 1 August 2014. Funding came from the NSF, DOE, and private funding raised by the private LSST Discovery Alliance. Operations are managed by the Association of Universities for Research in Astronomy (AURA). Construction cost was expected to be about $680 million.

Site construction began in April 2015. The first pixel with the engineering camera came in October 2024, while system first light images were released 23 June 2025. Full survey operations were planned to begin later in 2025, delayed by COVID-related issues.

Rubin is expected to catalog more than five million asteroids (including ~100,000 near-Earth objects), and image approximately 20 billion galaxies, 17 billion stars, and six million small Solar System bodies.

The telescope was originally named the Large Synoptic Survey Telescope, where the word synoptic—derived from the Greek words σύν (syn 'together') and ὄψις (opsis 'view')—describes observations that give a broad view of a subject. In June 2019, the observatory was renamed the Vera C. Rubin Observatory as proposed by United States Representative Eddie Bernice Johnson and Resident Commissioner of Puerto Rico Jenniffer González-Colón. The renaming was enacted as United States law on 20 December 2019, and announced at the 2020 American Astronomical Society winter meeting. The name honors Rubin and her colleagues' probes of the nature of dark matter by mapping and cataloging billions of galaxies through space and time.

The telescope itself is named the Simonyi Survey Telescope, in recognition of private donors Charles and Lisa Simonyi.