Prison Island, also known as Changuu Island, is a small island situated just off the coast of Stone Town in Zanzibar, Tanzania. This island holds historical significance and has become a popular destination for visitors exploring the Zanzibar Archipelago.

Originally intended as a prison in the 1860s, the British constructed a prison complex on the island, but it was later repurposed as a quarantine station for yellow fever cases. However, the prison was rarely used as intended, and instead, the island became a quarantine station for the entire region. One of the notable features of Prison Island is its population of Aldabra giant tortoises, originally gifted to the island in the late 19th century. These majestic creatures, some of which are over a hundred years old, roam freely on the island and have become a major attraction for visitors.

In addition to interacting with the giant tortoises, visitors can explore the island's historical remnants, including the old prison buildings, and enjoy the pristine beaches and crystal-clear waters ideal for swimming and snorkeling.

Boat trips to Prison Island are readily available from Stone Town and other points along the Zanzibar coast, offering a chance to experience the island's history, observe the giant tortoises up close, and enjoy the natural beauty of the area.

For tourists exploring Zanzibar, a visit to Prison Island provides an interesting blend of history, nature, and leisure activities, offering a unique experience within the archipelago.