The country is largely a low-lying coastal plain and has many rivers, some with wide swampy estuaries. The chief towns are Gabú, Oio, Cacheu, and Bolama. About half of the inhabitants adhere to traditional beliefs, and 45% are Muslim; there is a small Christian minority. The population is comprised mainly of five ethnic groups: the Balante, the Fulani, the Mandjack, the Mandinka, and the Papel. Portuguese is the official language, but Crioulo (a Portuguese creole) and a number of African languages are also spoken.

Guinea-Bissau is one of the world's poorest nations. Farming and fishing are the leading occupations; cashew nuts are the main cash crop, and rice, corn, beans, cassava, and cotton are grown for domestic use. The country's mineral resources, including phosphates, bauxite, granite, and limestone, are largely unexploited; however, prospecting for offshore petroleum deposits has begun. Industrial activity is mostly limited to the processing of agricultural products. Cashew nuts are by far the largest export; fish, seafood, peanuts, palm kernels, and timber are also exported. Imports include foodstuffs, machinery, transportation equipment, and petroleum products. The nation's location has also made a major transshipment point for the illegal drug trade from Latin American to Europe and the Middle East. The main trading partners are India, Italy, Senegal, Nigeria, and Portugal.

Guinea-Bissau is governed under the constitution of 1984 as amended. The president, who is the head of state, is popularly elected for a five-year term; there are no term limits. The prime minister, who is the head of government, is appointed by the president. The unicameral legislature consists of the 100-seat National People's Assembly, whose members are popularly elected for four-year terms. Administratively, Guinea-Bissau is made up of nine regions.

The area that became Portuguese Guinea was first visited by the Portuguese in 1446–47, and in the 16th cent. it was an important source of slaves sent to South America. The territory was administered as part of the Portuguese Cape Verde Islands possession until 1879, when it became a separate colony. In 1951 it was constituted an overseas province.

In 1956, Amilcar Cabral founded the African Party for the Independence of Guinea and Cape Verde (PAIGC). After some years of sporadic violence, the PAIGC launched a war of independence in Portuguese Guinea in the early 1960s; in 1973 it declared the province, renamed Guinea-Bissau, independent of Portugal. A government was established and elections for a national assembly were held in PAIGC-controlled areas. Following the coup in Portugal (1974), the new Portuguese government initiated negotiations with the PAIGC.

In Aug., 1974, an agreement was reached under which Portugal granted (Sept. 10) independence to Guinea-Bissau. Luis de Almeida Cabral (the brother of Amilcar Cabral, who had been assassinated in 1973) became the first president, and Guinea-Bissau was admitted to the United Nations that year. Although Portugal refused to give the Cape Verde Islands and Guinea-Bissau independence together (granting Cape Verde separate independence in 1975), the two maintained the PAIGC as a common political party for five years. Guinea-Bissau remained a single-party state with limited civil rights. Security was a primary concern in the early years of independence, as the regime was weak in Bissau where there was lingering support for the Portuguese.

In 1980 a coup brought João Bernardo Vieira to power. The new regime opposed unification with Cape Verde, but relations between the two nations were normalized in 1983. Although Vieira's regime in the 1980s was characterized by purgings of political enemies and suppression of dissent, he also introduced health reforms and initiatives to increase agricultural production and economic diversity. However, the economy did poorly and the country relied on outside aid to make up for enormous deficits. In 1991 the national assembly officially revoked the PAIGC's status as the sole legal party, and in 1994 Vieira was chosen as president in the country's first free elections.

An army mutiny began in June, 1998, eventually turning into a war in which neighboring Senegal and Guinea intervened on Vieira's behalf, but the coup almost marked the beginning of a period of economic and political troubles. In May, 1999, the military ousted Vieira and installed Malam Bacai Sanhá, the former head of parliament, as interim president. In Dec., 1999, two opposition parties won a majority in parliament, and, after defeating Sanhá in a runoff in Jan., 2000, Party for Social Renewal (PRS) candidate Kumba Yala won the presidency. An army rebellion in Nov., 2000, by former junta leader Gen. Ansumane Mane was crushed and Mane was killed. Yala, hampered by the poor economy and heading an unstable government, was ousted in Sept., 2003, by a military coup that subsequently received the support of many civilian leaders. Businessman Henrique Rosa was appointed president of a transitional national government. Parliamentary elections in Mar., 2004, resulted in a plurality for the PAIGC, and Carlos Gomes Júnior became prime minister with the support of the PRS. In October the chief of the armed forces was killed in a brief mutiny over back pay, but a peaceful end to uprising was negotiated.

Presidential elections were held in June, 2005, and were dominated by the candidacies of former presidents Vieira (who returned from exile), Sanhá, and Yala (who had originally been barred from political activity but was nominated by the PRS and was permitted to run). The month before the election Yala claimed to be the rightful president, revoking his "renunciation of power" and occupying the presidential palace. Although Yala's move came to nothing, it raised tensions in the nation. When he placed third in the June vote Yala claimed to have won nonetheless, but ended up accepting the results even as he denied them. A runoff between Sanhá, who placed first but failed to win a majority, and Vieira in July resulted in a win for Vieira. Sanhá asserted the vote was marred by fraud, and his party, the PAIGC, refused until September to recognize the result.

At the end of Oct., 2005, Vieira dismissed Gomes Júnior as prime minister, and then appointed Aristides Gomes, a political ally, to the post. In Mar., 2006, fighting erupted when government troops attempted to oust Casamance rebels from Senegal who had established bases in NW Guinea-Bissau. A no-confidence vote in Gomes's goverment in Mar., 2007, led to the appointment of Martinho N'Dafa Cabi, a PAIGC leader, to the post the next month. In July, 2007, the president, citing the nation's financial straits, rescheduled the Mar., 2008, parliamentary elections so that they would coincide with the 2009 presidential election.

See C. Lopes, Guinea-Bissau: From Liberation Struggle to Independent Statehood (1987); R. Lobban and J. Forrest, Historical Dictionary of the Republic of Guinea-Bissau (2d ed. 1988).