Carnley Harbour is a large natural harbour in the south of the Auckland Islands

Auckland Islands

The Auckland Islands are an archipelago of the New Zealand Sub-Antarctic Islands and include Auckland Island, Adams Island, Enderby Island, Disappointment Island, Ewing Island, Rose Island, Dundas Island and Green Island, with a combined area of...

, a subantarctic part of the New Zealand Outlying Islands

New Zealand Outlying Islands

The New Zealand outlying islands comprise nine island groups, located in the subtropics and subantarctic, which are part of New Zealand but lie outside of the New Zealand continental shelf. Although considered as integral parts of New Zealand, seven of the nine island groups are not part of any...

. Formed from the drowned crater of an extinct volcano

Volcano

2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...

, the harbour separates the mainland of Auckland Island

Auckland Island

Auckland Island is the main island of the Auckland Islands, an uninhabited archipelago in the south Pacific Ocean belonging to New Zealand. It is inscribed in the together with the other subantarctic New Zealand islands in the region as follows: 877-004 Auckland Isls, New Zealand S50.29 E165.52...

 from the smaller Adams Island

Adams Island, New Zealand

Adams Island is part of Auckland Islands archipelago. The southern end of Auckland Island broadens to a width of where a narrow channel, known as Carnley Harbour or the Adams Straits, separates it from the roughly triangular Adams Island , which is even more mountainous, reaching a height of at...

. The harbour is sometimes referred to as the Adams Straits.
The harbour is undeveloped (the Auckland Islands are uninhabited), and has three major arms: North Arm, Musgrave Bay, and Western Arm. Of these, the first two are deep indentations in the coast of Auckland Island; the last connects with Victoria Passage to form a channel separating Auckland and Adams Islands.