Scientists at the University of California, Santa Cruz and Caltech began development of a design that would eventually become the TMT, consisting of a 492-segment primary mirror with nine times the power of the Keck Observatory.

Due to its light-gathering power and the optimal observing conditions which exist atop Mauna Kea, the TMT would enable astronomers to conduct research which is infeasible with current instruments.

The TMT is designed for near-ultraviolet to mid-infrared (0.31 to 28 μm wavelengths) observations, featuring adaptive optics to assist in correcting image blur.

In July 2023 a new state appointed oversight board, which includes Native Hawaiian community representatives and cultural practitioners, began a five-year transition to assume management over Mauna Kea and its telescope sites, which may be a path forward.

"[21] An alternate site for the Thirty Meter Telescope has been proposed for La Palma, Canary Islands, Spain, but is considered less scientifically favorable by astronomers.

[23] The US National Academy of Sciences made a suggestion that a 30-meter (98 ft) telescope should be the focus of US astronomy interests and recommended that it be built within the decade.

[25] The TMT would have nine times the collecting area of the older Keck telescope using slightly smaller mirror segments in a vastly larger group.

[37][38] The Hawaii Board of Land and Natural Resources conditionally approved the Mauna Kea site for the TMT in February 2011.

[48] The IndiaTMT Optics Fabricating Facility (ITOFF) will be constructed at the Indian Institute of Astrophysics campus in the city of Hosakote, near Bengaluru.

Ramaprakash, the associate programme director of India-TMT, stated; "All sensors, actuators and SSAs for the whole telescope are being developed and manufactured in India, which will be put together in building the heart of TMT", also adding; "Since it is for the first time that India is involved in such a technically demanding astronomy project, it is also an opportunity to put to test the abilities of Indian scientists and industries, alike.

Based on these measurements, a pair of deformable mirrors will be adjusted many times per second to correct optical wave-front distortions caused by the intervening turbulence.

[62][63] This system will produce diffraction-limited images over a 30-arc-second diameter field-of-view, which means that the core of the point spread function will have a size of 0.015 arc-second at a wavelength of 2.2 micrometers, almost ten times better than the Hubble Space Telescope.

[64] Three instruments are planned to be available for scientific observations: In 2008, the TMT corporation selected two semi-finalists for further study, Mauna Kea and Cerro Amazones.

[73] Mauna Kea is the most sacred mountain in Hawaiian culture[73][74][75][76][77][78] as well as conservation land held in trust by the state of Hawaii.

[82][83][84] The project became the focal point of escalating political conflict,[85] police arrests[86][87][88] and continued litigation over the proper use of conservation lands.

[89][90] Native Hawaiian cultural practice and religious rights became central to the opposition,[91] with concerns over the lack of meaningful dialogue during the permitting process.

[94] On April 7, 2015, the construction was halted for one week at the request of Hawaii state governor David Ige, after the protest on Mauna Kea continued.

David Ige and the Thirty Meter Telescope International Observatory jointly announced that construction would begin the week of July 15, 2019.

The American Astronomical Society stated through their Press Officer, Rick Fienberg; "The Hawaiian people have numerous legitimate grievances concerning the way they’ve been treated over the centuries.

[120] On December 19, 2019, Hawaii Governor David Ige announced that the state would reduce its law enforcement personnel on Mauna Kea.

[122] Early in 2020, TMT and the Giant Magellan Telescope (GMT) jointly presented their science and technical readiness to the U.S. National Academies Astro2020 panel.

The panel has produced a series of recommendations for implementing a strategy and vision for the coming decade of U.S. Astronomy & Astrophysics frontier research and prioritize projects for future funding.

[126] The COVID-19 pandemic resulted in TMT's partnership working from home around the world and presented a public health threat as well as travel and logistical challenges.

On August 13, 2020, the Speaker of the Hawaii House of Representatives, Scott Saiki announced that the National Science Foundation (NSF) has initiated an informal outreach process to engage stakeholders interested in the Thirty Meter Telescope project.

[130][131] In July 2023 a new state appointed board, the Maunakea Stewardship Oversight Authority, began a five-year transition to assume management over the Mauna Kea site and all telescopes on the mountain.

[22] Other astronomers argue that construction of the telescope in La Palma would disrupt projected international collaboration between the United States and other involved countries such as Japan, Canada, and France.

[22] Environmentalists such as Ben Magec and the environmental advocacy organization Ecologistas en Acción in the Canary Islands are gearing up to fight against its construction there as well.

[22] On July 29, 2021, Judge Roi López Encinas of the High Court of Justice of the Canary Islands, revoked the 2017 concession of public lands by local authorities for the TMT construction.

[133] On July 19, 2022, The National Science Foundation announced it will carry out a new environmental survey of the possible impacts of the construction of the Thirty Meter Telescope at proposed building sites at both Mauna Kea and at the Canary Islands.

[134] Continued funding for the telescope will not be considered prior to the results of the environmental survey, updates on the project's technical readiness, and comments from the public.