To answer the PNC allegation that the existing electoral system unduly favoured the Indo-Guyanese community, the British government introduced for the elections of December 1964 a new system of proportional representation. Thereafter the PNC and a smaller, more conservative party formed a coalition government, led by Burnham, which took the colony into independence under its new name, Guyana, on May 26, 1966. The PNC gained full power in the general election of 1968, which was characterized by questionable rolls of overseas voters and widespread claims of electoral impropriety.

On February 23, 1970, Guyana was proclaimed a cooperative republic within the Commonwealth. A president was elected by the National Assembly, but Burnham retained executive power as prime minister. Burnham declared his government to be socialist and in the later 1970s sought to reorder the government in his favour. In 1978 one of the most bizarre incidents in modern history occurred in Guyana when some 900 members of a religious community known as the Peoples Temple committed mass suicide in their Jonestown commune at the behest of their leader, Jim Jones.

In 1980, under a new constitution that provided for a unicameral legislature, Burnham became executive president, with still wider powers, after an election in which international observers detected widespread fraud. Two major assassinations also occurred during this time—Jesuit priest and journalist Bernard Darke was killed in July 1979, and prominent historian and political leader Walter Rodney was murdered in June 1980. Many observers accused Burnham of involvement in the killings. In the following years Burnham faced an economy shattered by the depressed demand for bauxite and sugar and a restive populace suffering from severe commodity shortages and a near breakdown of essential public services. Burnham enforced austerity measures, and he began leaning toward Soviet-bloc countries for support. When he died in 1985, Burnham was succeeded by the prime minister, Hugh Desmond Hoyte, who pledged to continue Burnham’s policies. In elections held that year, Hoyte won the presidency by a wide margin, but once again charges of vote fraud were raised.

In the late 1980s Hoyte gradually shifted away from Burnham’s ideology, denouncing communism and granting more rights to the Guyanese. His administration, confronting worsening financial and economic problems, moved to liberalize the economy. He also bowed to pressure for electoral reform, and elections held in 1992 were considered free and fair by international observers. The PPP triumphed in the elections, and Jagan became president. In contrast to the strong socialist views he had held decades earlier, Jagan now advocated policies more conducive to democratization and economic reform. After Jagan’s death in 1997, his wife, Janet Jagan, was elected president in elections held later that year. The PNC disputed the results of the elections, however, and many demonstrations and protests ensued. Janet Jagan stepped down in 1999, attributing her resignation to ill health. Bharrat Jagdeo of the PPP was appointed president; he was reelected in 2001 and again in 2006.

Jagdeo’s administration was beset with numerous difficulties. The PNC staged more protests after the 2001 parliamentary elections, when it seemed to many that the PPP would continue to win control of the government simply because their constituency, mainly Indo-Guyanese, was the majority population in the country. A violent crime spree, fueled by political unrest, broke out in 2002 following the escape of five convicts from Georgetown Prison. In 2005 severe flooding killed dozens of people and destroyed large amounts of the rice and sugarcane crops.

Prospects brightened in September 2007 when a United Nations international tribunal settled a long-standing maritime boundary dispute between Guyana and Suriname by granting Guyana the far-larger share of the Guyana-Suriname Basin in contention. A new boundary was drawn, and soon afterward offshore oil exploration was begun there. Despite his apprehension, Jagdeo signed a trade agreement with the European Union in 2008; he hoped to increase economic stability and strengthen international relations. Guyana continued to struggle with violent crime, ethnic tensions, and episodic political unrest, but the economy improved, as the government invested in the agriculture and forestry sectors, in offshore oil exploration, and in new roads and bridges.

Jagdeo was constitutionally prohibited from running for a third term, and in November 2011 Donald Ramotar of the PPP was elected president. That year, however, his party and its junior coalition partner, the Civic Party, subsequently lost their majority in the National Assembly when a coalition was formed by A Partnership for National Unity (APNU)—an alliance comprising the People’s National Congress Reform (PNCR; a reconstituted PNC, including the former Reform Party) and several smaller parties—and the Alliance for Change (AFC) party. APNU-AFC’s single-vote majority, combined with the PPP’s continued control of the presidency, resulted in a period of legislative gridlock. In November 2014 Ramotar, fearing an imminent no-confidence vote in response to some $22.5 million of spending without parliamentary approval, prorogued parliament. Although the constitution allowed the president to suspend parliament for up to six months, the opposition accused him of acting dictatorially.

In the national election in May 2015 the combined APNU-AFC slate garnered some 207,000 votes compared with about 201,000 for the PPP, meaning that the presidency went to the coalition’s candidate, publisher and former general David Granger. Ramotar protested the results, but international observers declared the election to be free and fair.

The stakes in Guyanese politics were raised in 2015 by the discovery of a rich oil field in the country’s offshore waters. By the end of 2020, another 17 underwater fields had been discovered in Guyana’s Stabroek Block in the Atlantic, promising to transform the country’s economy into one of the fastest-growing in the world as Guyana entered a partnership with Exxon, which had made the discoveries. Both APNU-AFC and the PPP jockeyed for position to control the development of the new industry and the disposition of the wealth portended by the oil boom.

Criticized for not acting quickly enough to regulate the oil industry, Granger’s government lost a vote of confidence by the narrowest of margins (33–32) in December 2018. Instead of scheduling an election within the three-month period mandated by the constitution, however, the ruling coalition sought to have the vote of confidence overturned in the courts. Ultimately, its efforts proved futile, and, after much wrangling, an election was set for early March 2020. The election sparked its own controversy when Granger’s claim of victory was challenged in the wake of obvious election fraud. A 100-day-long national recount followed and revealed the PPP to have been the winner by a margin of about 15,000 votes. Once again APNU-AFC challenged the results in court, and for some five months Granger balked at handing over power. Finally, responding to intense international pressure, he stepped aside, and in early August 2020 Mohamed Irfaan Ali of the PPP became Guyana’s president.