The Thirty Meter Telescope protests are a series of protests and demonstrations that began on the Island of Hawaii in the United States over the choosing of Mauna Kea for the site location of the Thirty Meter Telescope. Mauna Kea is considered the most sacred mountain of Native Hawaiian religion and culture. Protests began locally within the state of Hawaii on October 7, 2014 but went global within weeks of the April 2, 2015 arrest of 31 people who had blockaded the roadway to keep construction crews off the summit.
The TMT, a ground-based, large segmented mirror reflecting telescope grew from astronomers' prioritization in 2000 of a thirty-meter telescope to be built within the decade. Mauna Kea was announced as TMT's preferred site in 2009. Opposition to the project began shortly after the announcement of Mauna Kea as the chosen site out of 5 proposals. While opposition against the observatories on Mauna Kea has been ongoing since the first telescope this protest may be the most vocal. The project was expected to be completed by 2024, nearly simultaneously with the 39-meter Extremely Large Telescope being built in Chile however, on December 2, 2015, the Supreme Court of Hawaii invalidated the TMT's building permits. The court ruled that due process was not followed. The TMT corporation then removed all construction equipment and vehicles from Mauna Kea, and re-applied for a new permit, meant to respect the Supreme Court's ruling. This was granted on September 28, 2018. On October 30, 2018, the Court validated the new construction permit.