Alexander Macmillan may refer to:

• Alexander MacMillan (publisher) (1818–1896), co-founder of Macmillan Publishers
• Alexander Macmillan, 2nd Earl of Stockton (born 1943), descendant and former chairman of Macmillan Publishers
• Alexander Hugh Macmillan (1877–1966), member of the Watch Tower Bible & Tract Society Board of Directors in 1918
• Alexander Stirling MacMillan (1871–1955), Canadian politician in Nova Scotia
• Alex McMillan (born 1932), American politician from North Carolina
• Alexander McMillan (North Carolina politician) (died 1817), American politician from North Carolina
• Alexander McMillan (Wisconsin pioneer) (1825–1901), American politician in Wisconsin
• Alexander Macmillan (born 1927), Canadian engineer