Alexander Mackintosh (2 October 1861 — 1945) was an American architect and architectural designer active in New York City from the 1890s until his death.

[1][2] Macintosh was born in London, England to Alexander Mackintosh and his wife, the former Elizabeth Smith.

[4] Mackintosh worked for prominent British architect Sir Aston Webb before immigrating to the United States in January 1893.

[5][6][7] After moving to the United States, he worked for Kimball & Thompson, a New York City firm, from 1893 until it disbanded in 1898, and then opened his own business.

Among the Kimball & Thompson projects on which Mackintosh worked were a French Renaissance Revival mansion for Gertrude Rhinelander Waldo (1898); alterations to the B. Altman department store (1896); and the Empire Building (1895).