The Giant Magellan Telescope (GMT) is a ground-based extremely large telescope under construction, as part of the US Extremely Large Telescope Program (US-ELTP), as of 2022. It will consist of seven 8.4 m (27.6 ft) diameter primary segments, that will observe optical and near infrared (320–25000 nm) light, with the resolving power of a 24.5 m (80.4 ft) primary mirror and collecting area equivalent to a 22.0 m (72.2 ft) one, which is about 368 square meters. The telescope is expected to have a resolving power 10 times that of the Hubble Space Telescope and four times that of the James Webb Space Telescope, although it will be unable to image in the same infrared frequencies available to telescopes in space. As of May 2021, six mirrors have been cast and the construction of the summit facility has begun.

A total of seven primary mirrors are planned, but it will begin operation with four. The US$1 billion project is US-led in partnership with Australia, Brazil, and South Korea, with Chile as the host country.