Alexander MacMillan (3 October 1818 – 25 January 1896), born in Irvine, Ayrshire, Scotland, was a cofounder, in 1843, with his brother Daniel of Macmillan Publishers. His family were crofters from the Isle of Arran.

Alexander was the partner who developed the literary reputation of the company while Daniel took charge of the business and commercial side. Originally called Macmillan & Co., the firm started as a successful bookshop in Cambridge. The brothers soon started publishing books as well as selling them. After Daniel's death in 1857, Alexander continued to run the firm. He expanded the company into a worldwide organization and also started publishing magazines, including the prestigious scientific journal Nature. Macmillan assigned George Edward Brett to create the New York office in August 1869 and hired American firm Messrs. Pott & Amery to assist in the marketing and distribution of Macmillan's books.

Alexander's brother Daniel was grandfather of Harold Macmillan, who became Prime Minister of the United Kingdom.

Macmillan Publishing

Macmillan was founded in 1843 by Daniel and Alexander Macmillan, two brothers from the Isle of Arran, Scotland. Daniel was the business brain, while Alexander laid the literary foundations, publishing such notable authors as Charles Kingsley (1855), Thomas Hughes (1859), Francis Turner Palgrave (1861), Christina Rossetti (1862), Matthew Arnold (1865) and Lewis Carroll (1865). Alfred Tennyson joined the list in 1884, Thomas Hardy in 1886 and Rudyard Kipling in 1890.

Other major writers published by Macmillan included W. B. Yeats, Rabindranath Tagore, Nirad c. Chaudhuri, Seán O'Casey, John Maynard Keynes, Charles Morgan, Hugh Walpole, Margaret Mitchell, C. P. Snow, Rumer Godden and Ram Sharan Sharma.

Beyond literature, the company created such enduring titles as Nature (1869), the Grove Dictionary of Music and Musicians (1877) and Sir Robert Harry Inglis Palgrave's Dictionary of Political Economy (1894–99).

George Edward Brett opened the first Macmillan office in the United States in 1869 and Macmillan sold its U.S. operations to the Brett family, George Platt Brett, Sr. and George Platt Brett, Jr. in 1896, resulting in the creation of an American company, Macmillan Publishing, also called the Macmillan Company. Even with the split of the American company from its parent company in England, George Brett, Jr. and Harold Macmillan remained close personal friends. Macmillan Publishers re-entered the American market in 1954 under the name St. Martin's Press.

Macmillan of Canada was founded in 1905; Maclean-Hunter acquired the company in 1973. Following numerous mergers, Macmillan Canada dissolved in 2002 after John Wiley & Co. acquired it.

After retiring from politics in 1964, former Prime Minister of the United Kingdom, Harold Macmillan, became chairman of the company, serving until his death in December 1986. He had been with the family firm as a junior partner from 1920 to 1940 (when he became a junior minister), and from 1945 to 1951 while he was in the opposition in Parliament.

Holtzbrinck Publishing Group purchased the company in 1999.