Mamoon Abdul Gayoom is the son of Abdul Gayoom Ibrahim (Maafaiygey Dhon Seedhi) and Khadheeja Moosa. His father had 25 children from 8 wives. He is the 11th child of his family.

He spent most of his youth in Egypt. He was part of a group of 15 students chosen at the initiative of Mohamed Amin Didi to get an education abroad. At the age of 10, in 1947, he embarked for Egypt. However, because of the troubles which led to the Arab-Israeli war of 1948–1949, his layover in Ceylon, scheduled to last several days, lasted for two and a half years during which he studied at the Buona Vista College, Galle and at Royal College, Colombo.

He eventually reached Egypt in March 1950, after the end of the conflict.

During his studies, he led a group of 14 Maldivian students who sent a letter to Prime Minister Ibrahim Nasir. They asked him to reconsider his Desire to establish diplomatic relations with Israel. Following this letter, their scholarships were removed and the students were taken under the care of the Egyptian government. This support stopped after graduation in 1966, however, and he was forced to end his studies.

In 1965, he met Nasreena Ibrahim, a student who had just arrived in Cairo from the Maldives for her studies. She was then 15 and he was 27. Four years later, they married in Cairo, on 14 July 1969. A few weeks after his marriage, he joined Ahmadu Bello University in Zaria, Nigeria as a lecturer in Islamic Studies and moved there with Nasreena. On 20 March 1970, Nasreena gave birth to twins, Dhunya Maumoon and Yumna Maumoon. Nasreena went back to Malé when expecting their third child. She gave birth to their first son, Ahmed Faris Maumoon, in Malé, on 31 March 1971. Nine years later, during abdul Gayoom's presidency, a second son, Ghassan, was born on 12 June 1980.

When his two-year contract with Ahmadu Bello University ended, he returned to the Maldives in 1971. Three weeks later, he joined the Aminiyya School as a Teacher of English, arithmetic and Islam. In 1972, he was appointed as the manager of the government shipping department.

On 12 March 1973, he was placed under house-arrest for criticising President Ibrahim Nasir's policies for having no human rights. He was tried in court and sentenced to banishment for four years on 14 May 1973. On 21 May, he was taken to Makunudhoo Island of Haa Dhaalu Atoll. he was released on 13 October 1973, after serving only five months, as a result of an amnesty following Nasir's re-election for a second five-year term.

On 28 July 1974, he was again arrested for criticising Nasir's policies. This time he was kept in solitary confinement in a prison in Malé nicknamed the 'China Garden', as Chinese fishermen were once detained there. This prison was later demolished during Gayoom's presidency and the Islamic Centre was erected on the site. After 50 days in jail, he was set free, in September 1974.

Six weeks later, he was appointed special undersecretary in the office of Prime Minister Ahmed Zaki. The post of Prime Minister was abolished with the removal and banishment of Ahmed Zaki from office, on 6 March 1975. With this decision, his position vanished as well. However, when he returned from Colombo, he was made the Deputy Ambassador of the Maldives to Sri Lanka. In 1975, he was sent to the United Nations for two months as a member of the Maldives delegation, part of the department of External Affairs (as the Foreign Ministry was then called). After nine weeks, he was appointed the Deputy Minister of Transport. One year later, he was tenured at the United Nations from September 1976 to January 1977. On 29 March 1977, Gayoom was appointed Minister of Transport, making him a member of Nasir's cabinet. He held the post until 10 November 1978.

Five months later, he was elected the new President of the Maldives, with 92.96% of the votes. The grand reception of his inauguration was held at Majeediyaa School on the night of 10 November 1978. In a 1983 referendum, he was re-elected on 30 September for a second term, polling a record 95.6%. On 23 September 1988, he was re-elected for a third term with 96.4% of the popular vote. On 1 October 1993, he was elected for a fourth term with 92.76% of the popular vote. On 16 October 1998, he was elected for an unprecedented fifth term of office, this time with 90.9% of the popular vote. He was last re-elected to a sixth five-year term in October 2003 with 90.28% of the vote. In all cases, he was the sole candidate, having been nominated by the Majlis.

In a 2007 referendum, voters approved a presidential system with direct election of the President rather than a parliamentary system. This was the option favored by Abdul Gayoom.

The October 2008 Maldivian presidential election was the first presidential election Maumoon Abdul Gayoom allowed to be contested. Standing as the DRP candidate, he lost in the election's second round, in which he received 45.75% of the vote against 54.25% for his opponents, MDP's Presidential Candidate Mohamed Nasheed accordingly succeeded Abdul Gayoom as President on November 11, 2008, with Gaumee Itthihaad's Candidate Dr. Mohammed Waheed Hassan in the new post of Vice President.

In July 2016, Maumoon due to disagreements between President Abdulla Yameen and Maumoon, the party split into two factions. Later in October 27, Maumoon withdrew his support for President Abdulla Yameen and joined the Maldives United Opposition.

Gayoom was arrested on 5 February 2018, for allegedly conspiring to overthrow the government along his son-in-law Moamed Nadheem. Maumoon son, Farish Maumoon, was repeatedly arrested and released and arrested again a day after his release. Maldivian Democracy Network reported Maumoon and Farish were being tortured by not allowing medical treatment.

Abdul Gayoom’s opponents and international human rights groups had accused him of employing terror tactics against dissidents, such as arbitrary arrests, detention without trial, employing torture, forced confessions, and politically motivated killings.