The term Sky Island (空島, Sorajima?) can refer to any island located in the sky. Known Sky Islands include:
- Skypiea (consists of Angel Island, Upper Yard, and Shandora)
- Birka
- Weatheria
Urouge's homeland is also a sky island, although the name of the island was not stated.
At some point Bellamy went to Skypiea, and returned with a pillar of gold.
The existence of sky islands are largely mocked or ignored by many; to those living in the Blue Sea the idea of an island in the sky seems illogical, impossible, or unbelievable. Travelling to a sky island is difficult due to their location, although not entirely impossible. One way is to ride a current known as the Knock Up Stream. Gan Fall mentioned another way to get to the sky Islands, which he called the "Summit of High West", but it is unknown as to what it actually is.