The Mariana Islands (; also the Marianas; in Chamorro: Manislan Mariånas) are a crescent-shaped archipelago comprising the summits of fifteen longitudinally oriented, mostly dormant volcanic mountains in the northwestern Pacific Ocean, between the 12th and 21st parallels north and along the 145th meridian east. They lie south-southeast of Japan, west-southwest of Hawaii, north of New Guinea and east of the Philippines, demarcating the Philippine Sea's eastern limit. They are found in the northern part of the western Oceanic sub-region of Micronesia, and are politically divided into two jurisdictions of the United States: the Commonwealth of the Northern Mariana Islands and, at the southern end of the chain, the territory of Guam. The islands were named after the influential Spanish queen Mariana of Austria following their colonization in the 17th century.

The indigenous inhabitants are the Chamorro people. Archaeologists in 2013 reported findings which indicated that the people who first settled the Marianas arrived there after making what may have been at the time the longest uninterrupted ocean voyage in human history. They further reported findings which suggested that Tinian is likely to have been the first island in Oceania to have been settled by humans.

Spanish expeditions, beginning with one by Portuguese explorer Ferdinand Magellan in the early 16th century, were the first Europeans to arrive; eventually, Spain annexed and colonized the archipelago, establishing their capital on the largest island, Guam. The Marianas were the first islands Magellan encountered after traversing the Pacific from the southern tip of South America. The fruits found there saved the survivors from scurvy, which had already killed dozens of crewmembers.