The lighthouse tower at Sumburgh head will open to visitors this weekend.
Public tours start on Saturday and will run between Friday and Sunday until the end of September.
The trust said it is “a key milestone” in the restoration of the lighthouse site.
A ceremony will be held to mark the occasion, with guests – including ex-lighthouse keepers who were based at Sumburgh Head – having the chance to take the tour.
Access to the fully functioning tower has been possible through the help of the Northern Lighthouse Board, which carried out alterations to the lightroom to ensure the safety of the light and visitors.
Tours will be held between noon and 3.20pm with tickets from the visitor centre gift shop.
The Sumburgh Head Lighthouse was designed by Robert Stevenson and built in 1821 and the light is controlled and maintained by the Northern Lighthouse Board as part of their on-going work to ensure the safety of mariners.
The £5.4 million lighthouse restoration project includes a new visitor centre, wildlife information and learning area.