John MacLennan Buchanan, PC QC (born April 22, 1931) is a Canadian lawyer and former politician who served as the 20th Premier of Nova Scotia from 1978 to 1990 and as a member of the Senate of Canada from 1990 to 2006.
Buchanan was born in Sydney, Nova Scotia. He graduated from Mount Allison University in 1954 with a Bachelor of Science degree and a Certificate in Engineering. He then went on to study at Dalhousie Law School and after graduating in 1958 entered the practice of law where he was appointed Queen's Counsel in 1972 and awarded Doctorates from Nova Scotia Technical College, Mount Allison University, Saint Mary's University, St. Francis Xavier University, and Université Saint Anne.
Buchanan was elected as a Member of the Nova Scotia Legislative Assembly in 1967, re-elected in 1970, 1974, 1978, 1981, 1984 and 1988. He was appointed to the Executive Council of Nova Scotia as Minister of Public Works and Fisheries in 1969. He was elected leader of the Progressive Conservative Party of Nova Scotia in 1971. Buchanan was elected as Premier of Nova Scotia in 1978. He was re-elected in 1981, 1984 and 1988, becoming the third Premier in Nova Scotia to be elected to four consecutive terms (following George Henry Murray and Robert Stanfield), and the fourth longest serving premier in the history of the province. On April 17, 1982, Buchanan was made a member of Her Majesty’s Privy Council. His biggest majority came in the 1984 election, when he led his party to victory, capturing 42 of the 52 seats in the legislature.
Buchanan resigned as Premier when he was appointed to the Senate of Canada by Brian Mulroney on September 12, 1990. Buchanan sat as a Progressive Conservative senator until 2004, when the party merged with the Canadian Alliance. He sat as a member of the Conservative Party of Canada from 2004 until his retirement at age 75 on April 22, 2006.
After Buchanan resigned as premier, it was revealed that he had secretly received $431,290 in funds in addition to his salary. A subsequent RCMP investigation concluded that there was no evidence to support criminal charges.
He married Mavis Forsyth in September 1954, and they had five children.