Fiske, John (1842–1901), a United States philosopher and historian. Fiske popularized the ideas on evolution of Charles Darwin and Herbert Spencer. In his most important work, Outlines of Cosmic Philosophy (1874), he attempted to show that societies developed by the same evolutionary process that Darwin described for biological organisms. He also wrote extensively on United States history; his best-known historical work is Critical Period of American History (1888).

Fiske was born in Hartford, Connecticut. He changed his name from Edmund Fisk Green to that of his maternal great-grandfather, John Fisk, in 1855, adding the “e” five years later. He graduated from Harvard University in 1863, and from Harvard Law School in 1865. He taught philosophy at Harvard, 1869–71, and served there as assistant librarian, 1872–79. He then had a highly successful career as a historian and a public lecturer.