The Hawaii Department of Land and Natural Resources has issued a notice to proceed (NTP) to the University of Hawaii for the $1.4bn Thirty Meter Telescope (TMT) on the peak of Mauna Kea.
It means all pre-construction conditions and mitigation measures have been met. The NTP is a condition of a Conservation District Use Permit (CDUP).
The University and relevant agencies are discussing a start date for construction.
It wants to build the TMT on the 14,000ft-high summit of the dormant volcano where the absence of air and light pollution improves observation.
But ancient Hawaiian law allows only high-ranking tribal chiefs to visit the peak, and protests broke out when construction initially began in 2014.
Henry Yang, from the TMT board of governors, said: "TMT is pleased and grateful that the notice to proceed has been issued by the Department of Land and Natural Resources to the University of Hawaii.
"We remain committed to being good stewards of Mauna Kea, and to honouring and respecting the culture and traditions of Hawaii. It has been a long process to get to this point.
"We are deeply grateful to our many friends and community supporters for their advice and for their encouragement and support of the TMT project over the years."
Image courtesy of Thirty Meter Telescope