McAdam or MacAdam is a surname with origins in the Ayrshire and Galloway regions of Scotland. Notable people with the surname include:

• John Loudon McAdam (1756-1836), a Scottish engineer noted for inventing the process of "macadamization" of roads.
• John McAdam (businessman), an American businessman
• John McAdam (politician) (1807-1893), Irish-born politician in New Brunswick, Canada
• John Macadam (1827-1865), an Australian (Scottish-born) chemist, medical teacher and politician, after whom the Macadamia nut is named
• David MacAdam (1910-1998), an American color scientist
• Doug McAdam (born 1951), an American sociologist studying social movements
• Colin McAdam (novelist), a Canadian novelist
• Elliot McAdam (born 1951), an Australian politician and Northern Territory Cabinet member
• Sean McAdam, an American baseball writer
• Adrian McAdam (born 1971), Australian Rules footballer
• Gilbert McAdam (born 1967), Australian Rules footballer
• Greg McAdam (born 1961), Australian Rules footballer
• Patrick "Pat" MacAdam is a Canadian writer