The Marshall Islands officially the Republic of the Marshall Islands (RMI), is a Micronesian nation of atolls and islands in the middle of the Pacific Ocean, just west of the International Date Line and just north of the Equator.

This nation of roughly 62,000 persons is located north of Nauru and Kiribati, east of the Federated States of Micronesia, and south of the U.S. territory of Wake Island, to which it lays claim.

From 1946 to 1958, as the site of the Pacific Proving Grounds, the U.S. tested 66 nuclear weapons in the Marshall Islands, including the largest nuclear test the U.S. ever conducted, Castle Bravo. Nuclear claims between the U.S. and the Marshall Islands are ongoing, and health effects from these tests linger. Project 4.1 was a medical study conducted by the United States of those residents of the Bikini Atoll exposed to radioactive fallout.

In 1979, the Government of the Marshall Islands was officially established and the country became self-governing.

In 1986, the Compact of Free Association with the United States entered into force, granting the Republic of the Marshall Islands (RMI) its sovereignty. The Compact provided for aid and U.S. defense of the islands in exchange for continued U.S. military use of the missile testing range at Kwajalein Atoll. The independence procedure was formally completed under international law in 1990, when the UN officially ended the Trusteeship status.

The country consists of 29 atolls and 5 isolated islands. The atolls and islands form two groups: the Ratak Chain and the Ralik Chain (meaning "sunrise" and "sunset" chains). 24 of them are inhabited.

The climate is hot and humid, with a wet season from May to November. The islands occasionally suffer from typhoons. Many Pacific typhoons start in the Marshall Islands region and grow stronger as they move west toward the Mariana Islands and the Philippines.