The Marshall Islands consist of two chains of coral atolls, together with more than 1,000 islets, just north of the Equator.
The atolls are coral deposits on the crater rims of submerged volcanoes.
The islands were occupied by the US for several decades after the Second World War. They are now a sovereign nation under a Compact of Free Association with the US which came into force in 1986 and was renegotiated in 2003.
The US controls the security and defence of the islands and provides millions of dollars in aid every year. The US rents the Kwajalein atoll as a base and missile test range.
The legacy of the post-war US occupation is seen particularly starkly on Bikini and Enewetak, which were both used for nuclear weapons testing between 1946 and 1958.
Climate change threatens the very existence of the islands. Many atolls lie barely a metre above sea level and are at risk being engulfed by rising waters.
Republic of the Marshall Islands
Area 181 sq km (70 sq miles)
Major languages Marshallese, English
Major religion Christianity
Life expectancy 67 years (men), 71 years (women)
Currency US dollar
President: Hilda Heine
Former education minister Hilda Heine made history in January 2016 by becoming the first female president of an independent Pacific island state.
She was elected to parliament at the November 2015 election in a group of independents that held the balance of power between the supporters of President Christopher Leoak and the opposition KEA party.
Parliament first chose Carsten Nemra as president, but an opposition-independent alliance forced him out in a no-confidence vote, proposing Ms Heine instead.
The first Marshallese woman to earn a PhD, she has a background in education and a record of campaigning on women's and climate-change issues.
The government generally respects media freedom. A privately-owned weekly is published in English and Marshallese.
A government monthly contains official news but avoids politics.
State-owned and private radios offer diverse views. US forces radio and TV can be received in some areas and US TV is available via cable. BBC World Service broadcasts in Majuro on 98.5 FM.
Some key dates in the history of the Marshall Islands:
Circa 2000 BC - First Micronesian navigators arrive in the Marshall Islands, naming the atolls Aelon Kein Ad - "our islands". They are skilled navigators able to make long canoe voyages among the atolls.
1521-29 - Portuguese navigator Ferdinand Magellan and Spaniard Miguel de Saavedra visit the islands.
1788 - The Marshall Islands are given their name by British Naval Captain John William Marshall who sails through the area with convicts bound for New South Wales.
1885 - Germany annexes the Marshall Islands, compensating Spain, which possessed the territory.
1914 - Japan captures the islands and builds several large military bases there.
1920 - League of Nations grants Japan a mandate to administer the territory.
1944 - US forces capture islands from the Japanese.
1946 - US begins a nuclear weapons testing programme on Bikini Atoll.
1947 - Islands become part of the Trust Territory of the Pacific Islands created by the UN and administered by the US.
1979 - Independence.