The Mariana Islands (also the Marianas; up to the early 20th century sometimes called Islas de los Ladrones meaning "Islands of Thieves") are a group of islands made up by the summits of 15 volcanic mountains in the western Pacific Ocean.
They are the southern part of a submerged mountain range that goes on for 1,565 miles (2,519 km) from Guam to near Japan. The Marianas are the northernmost islands of a larger island group called Micronesia. The Marianas have a total land area of 396 square miles (1026 km²) and are composed of two administrative units:
- Guam is a US territory
- the Northern Mariana Islands (including the islands of Saipan, Tinian and Rota) comprise a Commonwealth of the United States .