As of 2026-10-12, Thirty Meter Telescope tops the list with 66 m.
- #1 Thirty Meter Telescope — 66 m
future observatory in the United States
The Thirty Meter Telescope (TMT) is a proposal for an extremely large telescope (ELT), intended to be built on Mauna Kea, on the island of Hawai'i. Read more on Wikipedia.
Wikidata - #2 Gran Telescopio Canarias — 10 m
reflecting telescope at the Roque de los Muchachos Observatory
The Gran Telescopio Canarias is a 10.4 m (410 in) reflecting telescope located at the Roque de los Muchachos Observatory on the island of La Palma, in the Canary Islands, Spain. It is the world's largest single-aperture optical telescope. Read more on Wikipedia.
Wikidata - #3 Subaru Telescope — 8.20 m
Japanese telescope and observatory
Subaru Telescope is the 8.2-metre (320 in) telescope of the National Astronomical Observatory of Japan, located at the Mauna Kea Observatory on Hawaii. It is named after the open star cluster known in English as the Pleiades. It had the largest monolithic primary mirror in the world from its commissioning until the Large Binocular Telescope opened in 2005. Read more on Wikipedia.
Wikidata - #4 BTA-6 — 6.05 m
Large telescope in Russia
The BTA-6 is a 6-metre (20 ft) aperture optical telescope at the Special Astrophysical Observatory located in the Zelenchuksky District of Karachay-Cherkessia on the north side of the Caucasus Mountains in southern Russia. Read more on Wikipedia.
Wikidata - #5 Lowell Discovery Telescope — 4.30 m
observatory
The Lowell Discovery Telescope (LDT), formerly the Discovery Channel Telescope (DCT), is a 4.3 m (170 in) aperture telescope owned and operated by Lowell Observatory. The LDT was built at a dark sky site in the Coconino National Forest near Happy Jack, Arizona. Happy Jack is located at an elevation of 2,360 m (7,740 ft) and is approximately 65 km (40 mi) south-south-east of Flagstaff. The project was initially a partnership between Discovery Communications and Lowell Observatory. The... Read more on Wikipedia.
Wikidata - #6 VISTA — 4.10 m
astronomical telescope at Paranal Observatory
The VISTA is a wide-field reflecting telescope with a 4.1 metre mirror, located at the Paranal Observatory in Chile. It is operated by the European Southern Observatory and started science operations in December 2009. VISTA was conceived and developed by a consortium of universities in the United Kingdom led by Queen Mary University of London and became an in-kind contribution to ESO as part of the UK's accession agreement, with the subscription paid by the UK Science and Technology Facilities... Read more on Wikipedia.
Wikidata - #7 Víctor M. Blanco Telescope — 4.02 m
telescope located in Chile
The Víctor M. Blanco Telescope, also known as the Blanco 4m, is a 4-metre aperture telescope located at the Cerro Tololo Inter-American Observatory, Chile on the summit of Mt. Cerro Tololo. Commissioned in 1974 and completed in 1976, the telescope is identical to the Mayall 4m telescope located on Kitt Peak. In 1995 it was dedicated and named in honour of Puerto Rican astronomer Víctor Manuel Blanco. It was the largest optical telescope in the Southern hemisphere from 1976 until 1998, when... Read more on Wikipedia.
Wikidata - #8 Nicholas U. Mayall Telescope — 4.00 m
four-meter reflector telescope
The Nicholas U. Mayall Telescope, also known as the Mayall 4-meter Telescope, is a four-meter reflector telescope located at the Kitt Peak National Observatory in Arizona and named after Nicholas U. Mayall. It saw first light on February 27, 1973, and was the second-largest telescope in the world at that time, between the Hale and Shane (3 m). Initial observers included David Crawford, Nicholas Mayall, and Arthur Hoag. It was dedicated on June 20, 1973 after Mayall's retirement as director.... Read more on Wikipedia.
Wikidata - #9 3.6m Devasthal Optical Telescope — 3.60 m
Optical Telescope
The 3.6m Devasthal Optical Telescope (DOT) is a clear-aperture Ritchey–Chrétien telescope built by Aryabhatta Research Institute of Observational Sciences (ARIES), located at the Devasthal Observatory site, near Nainital, Kumaon, India. ARIES operates another 1.3m telescope at the same location. The telescope was activated remotely on 31 March 2016 by Indian Prime Minister Narendra Modi and Belgian Prime Minister Charles Michel from Brussels. The telescope optics were built in collaboration... Read more on Wikipedia.
Wikidata - #10 Galileo National Telescope — 3.58 m
3.58m Italian telescope
The Galileo National Telescope, is a 3.58-meter Italian telescope, located at the Roque de los Muchachos Observatory on the island of La Palma in the Canary Islands, Spain. The TNG is operated by the "Fundación Galileo Galilei, Fundación Canaria", a non-profit institution, on behalf of the Italian National Institute of Astrophysics (INAF). The telescope saw first light in 1998 and is named after the Italian astronomer Galileo Galilei. Read more on Wikipedia.
Wikidata