Ripapa Island, located off the shore of Lyttelton Harbour, has been closed since the February 22, 2011, earthquake.
But now visitors have a chance to access and explore the island and learn about its stories over summer.
The reopening was celebrated on Wednesday by Te Hapū o Ngāti Wheke and Minister of Conservation Eugenie Sage.
Residents and Lyttelton Primary School pupils retraced the footsteps of Ngāti Wheke ancestors during the event.
Said Ms Sage: “I am delighted to join Ngāti Wheke and DOC in officially welcoming some of the first visitors back to this tōpuni site.”
“The island has a rich and often fraught history which is largely unknown by New Zealanders," Ms Sage said.
"I hope many people take the opportunity to visit this summer and share the stories of what they learn with their whanau.
“Originally the South Island’s first musket fortified pā in the early 19th century, Ripapa Island was later used as a quarantine zone for immigrants and a prison for 150 Parihaka prisoners.
"For the past 131 years, it has been home to the Fort Jervois - the country’s most complete ‘Russian Scare’ fort, featuring rare ‘disappearing guns’.”
Ngāti Wheke spokesperson Yvette Couch-Lewis said mana whenua formally reopened and blessed Ripapa in July to ensure the island’s spirit was safe for future visitors.
“A tōpuni was placed over Ripapa in recognition of the significant cultural, spiritual, historic and traditional values of the island for mana whenua.”
