- _Gran Telescopio Canarias_ (GTC), La Palma, Canary Islands, Spain: 10.4-meter primary mirror
- _Very Large Telescope_ (VLT), Paranal Observatory, Chile: Four 8.2-meter primary mirrors that can work together as one (interferometry).
- _Subaru Telescope_, Mauna Kea, Hawaii, USA: 8.2-meter primary mirror
- _Gemini North Telescope_, Mauna Kea, Hawaii, USA: 8-meter primary mirror
- _Gemini South Telescope_, Cerro Pachón, Chile: 8-meter primary mirror
- _Large Binocular Telescope_ (LBT), Mount Graham, Arizona, USA: two 8.4-meter primary mirrors that can work together (interferometry).
- _Multiple Mirror Telescope_ (MMT), Mount Hopkins, Arizona, USA: six 1.8-meter primary mirrors that can work together (interferometry).
Largest Radio Telescopes in World:
- _Five-hundred-meter Aperture Spherical Telescope_ (FAST), Pingtang County, Guizhou Province, China: 500-meter diameter spherical dish.
- _Arecibo Observatory_, Arecibo, Puerto Rico, USA: 305-meter diameter dish
- _Green Bank Telescope_, Green Bank, West Virginia, USA: 100-meter diameter dish.
- _Effelsberg Radio Telescope_, Bad Münstereifel, Germany: 100-meter diameter dish.
Largest Space Telescopes in World:
- _James Webb Space Telescope_ (JWST), in space: Primary mirror consisting of 18 hexagonal, gold-plated beryllium segments measuring 6.5 meters in diameter when fully deployed.
- _Hubble Space Telescope_ (HST), in orbit around Earth: 2.4-meter primary mirror
- _Chandra X-ray Observatory_, in orbit around Earth: 1.2-meter primary mirror.
- _XMM-Newton Observatory_, in orbit around Earth: 0.75-meter primary mirror.
- _Gaia Observatory_, in orbit around the Sun at the L2 Lagrange point: 1.45-meter primary mirror.
