John Buchanan may refer to:
- John Buchanan (Canadian politician) (1931–2019), Premier of Nova Scotia, 1978–1990.
- John Buchanan (American politician), American journalist and U.S. presidential candidate, 2004
- John Buchanan (Maryland judge) (1772–1844), Chief Judge of the Maryland Court of Appeals
- John Buchanan (MP) (1761–1839), Scottish politician, MP for Dunbartonshire 1821–26
- John Buchanan (New Zealand politician) (1819–1892), New Zealand politician
- John A. Buchanan (1843–1921), US House of Representatives member from Virginia
- John Alexander Buchanan (1887–1976), Canadian senator
- John Andrew Buchanan (1863–1935), judge and politician in Astoria in the U.S. state of Oregon
- John C. Buchanan (Texas politician), Texas state senator, 1879–1885, see Eighteenth Texas Legislature
- John C. Buchanan (Virginia politician), Virginia state senator, 1972–1991
- John Hall Buchanan Jr. (1928–2018), US House of Representatives member from Alabama
- John P. Buchanan (1847–1930), Governor of Tennessee
- John Preston Buchanan (1888–1937), American politician in the Virginia Senate
- J. W. Buchanan (1871–1941), Arizona politician, state senator, state house of representatives
- John Buchanan (English cricketer) (1887–1969), English cricketer and decorated WWI officer
- John Buchanan (Australian cricketer) (born 1953), Australian cricketer and coach
- John Buchanan (Cambuslang footballer) (fl. 1889), Scottish footballer
- John Buchanan (footballer, born 1899) (1899–1947), Scottish footballer (St Mirren, Rangers, Morton)
- John Buchanan (footballer, born 1928) (1928–2000), Scottish footballer (Clyde)
- John Buchanan (footballer, born 1935) (1935–2009), Scottish footballer (Hibernian)
- John Buchanan (footballer, born 1951), Scottish footballer (Cardiff City, Northampton Town)
- John Buchanan (sailor) (1884–1943), British Olympic gold medalist in 1908
- John Buchanan (soccer), former Canadian soccer coach, in the Canadian Soccer Hall of Fame
- James Buchanan (1791–1868), US President commonly misreferenced as "John"