Belize evolved through several stages of decolonization, from universal adult suffrage in 1954 to a new constitution and internal self-government in 1964, when George Price, a middle-class Roman Catholic intellectual of mixed Creole and mestizo ancestry, became premier. (Price became leader of the PUP in 1954.) Unrelenting Guatemalan hostility, however, impeded independence. In the 1970s Belize took its case for self-determination to the international community, appealing to the United Nations (UN) and joining the Nonaligned Movement (see neutralism). Although the dispute between Guatemala and Great Britain remained unresolved, Belize became independent on September 21, 1981, with a British defense guarantee, and was admitted to the UN. The British military presence was withdrawn in 1994, and border security became the sole responsibility of the Belize Defence Force, which had been created in 1978. By the early 1990s Guatemala had formally recognized Belize as an independent state, and Belize had joined the Organization of American States (OAS); however, the territorial dispute heated up again in the late 1990s. In 2002 an OAS-assisted facilitation process formally proposed a solution, but Guatemala refused to accept it. In 2005 the two countries agreed that if a negotiated settlement proved to be impossible, the dispute could be settled by an international legal entity. In 2008 the governments of Belize and Guatemala agreed to submit their case to the International Court of Justice, subject to referenda in both countries.

In domestic politics the United Democratic Party (UDP), formed in 1973 and led by Manuel Esquivel, won the general election in 1984, but in 1989 the PUP won the election and Price again became prime minister (as the office was now called). The UDP won in a close election in 1993, and Esquivel again assumed leadership. In 1998, however, the PUP won by a landslide and its new leader, Said Musa, became prime minister.

Musa’s decision to raise taxes to pay off foreign debt sparked riots throughout Belize in 2005, and his administration was accused of corruption. The UDP, now led by Dean Barrow, triumphed in the 2008 general elections, and Barrow became the country’s first black prime minister. His party promised to end crime and government corruption and to create an elected Senate. Although a democratic tradition has been established in Belize, the country has struggled to develop under a dependent economy, and it has been pressured politically by the pervasive influence of the United States. The discovery of abundant quantities of oil near the Mennonite community at Spanish Lookout in the early 2000s was a boon for the country’s ailing economy, but, because Belize has no oil refineries, most of its crude oil is exported to the United States.

In July 2010 Barrow’s government introduced a controversial ninth amendment to the constitution to give the state majority ownership of public utilities. In April it had proposed an eighth amendment, which included preventive detention to combat a surge in violent crimes, but public opposition forced that measure to be placed on hold, and by July it had been abandoned. Meanwhile, the ninth—subsequently renamed eighth—amendment passed both houses of the legislature and was enacted in late October.

In elections on March 7, 2012, Barrow’s UDP government retained power. The UDP was also victorious in municipal elections. Following negotiations with creditors, in 2013 the government restructured its $550 million “superbond” debt at a cost of about $750,000 with a maturity date of 2038. In a snap election in November 2015, Barrow and the UDP triumphed again, winning an unprecedented third term, but, when Belizeans returned to the polls in November 2020, they ousted the UDP and replaced it with a People’s United Party (PUP) government headed by John Briceño.