Mahathir bin Mohamad (Jawi:محاضير بن محمد; born 10 July 1925) is a Malaysian politician, author, and physician who served as the fourth and seventh prime minister of Malaysia. He held office from 1981 to 2003 and later from 2018 to 2020 for a cumulative total of 24 years, making him the country's longest-serving prime minister. Before becoming premier, he served as deputy prime minister and in other cabinet positions. He was a member of Parliament for Langkawi from 2018 to 2022, Kubang Pasu from 1974 to 2004, and Kota Star Selatan from 1964 to 1969. His political career spanned more than 75 years, from joining protests opposing citizenship policies for non-Malays in the Malayan Union in the 1940s to forming the Gerakan Tanah Air coalition in 2022.

Born and raised in Alor Setar, Kedah, Mahathir excelled at school and became a physician. He became active in the United Malays National Organisation (UMNO) before entering the parliament of Malaysia in 1964. He served one term before losing his seat, subsequently falling out with Prime Minister Tunku Abdul Rahman and being expelled from UMNO. In 1970, he released the book The Malay Dilemma. When Abdul Rahman resigned, Mahathir re-entered UMNO and parliament, and was promoted to Minister of Education from 1974 to 1978 and Minister of Trade and Industry from 1978 to 1981. He became deputy prime minister in 1976 before being sworn in as prime minister in 1981, succeeding Hussein Onn.

During Mahathir's first tenure, Malaysia underwent modernisation and economic growth, and his government initiated widespread industry privatisation and a series of bold infrastructure projects. Mahathir was a dominant political figure, winning five consecutive general elections and fending off several rivals for UMNO's leadership. He centralised power through undermining judicial independence and supporting a constitutional amendment to remove legal immunity for royalty. He continued pro-bumiputera policies, and oversaw Malaysia's relatively fast recovery from the 1997 Asian financial crisis. In 1987, he detained various activists and religious figures under Operation Lalang, and in 1998 had his deputy Anwar Ibrahim arrested. His record of authoritarianism and curtailment of civil liberties strained relationships with the West. As prime minister, he was an advocate of Asian values and development models, and was particularly prominent across the Muslim world.

Mahathir unexpectedly stepped down in 2003, but remained politically influential and was critical of his successors. He quit UMNO over the 1MDB corruption scandal in 2016, joining BERSATU and leading the Pakatan Harapan opposition coalition to victory in the 2018 general election. During a second tenure as prime minister, he pledged to investigate the 1MDB scandal, combat corruption, and cut spending on large infrastructure projects. He also secured the pardon and release of Anwar Ibrahim. Mahathir resigned in 2020 amidst a political crisis. Despite losing his parliamentary seat in the 2022 general election, he remained active in politics and shifted party affiliation several times.

Mahathir's political views have shifted during his life, and are shaped by his Malay nationalism and Islamic religious beliefs.