The world’s most expensive private island that we could locate is Niihau, Hawaii. The island is referred to as ‘the forbidden island’ and is Hawaii’s smallest inhabited island.

There are roughly 250 residents of the 72 square mile island who live without roads, hotels, restaurants and electricity.

The island is a native Hawaiian preserve and it is the only island in the state where the primary language is still Hawaiian.

Niihau is owned by the Robinson family of Kaua’i and is estimated to be worth $100 million USD.