William Fairfield Warren (13 March 1833 – December 7 1929) was the first president of Boston University.

Born in Williamsburg, Massachusetts, he graduated at Wesleyan University, Middletown, Conn. (1853), and studied at Andover Theological Seminary and at Berlin and Halle. He entered the New England Conference in 1855 and was professor of systematic theology in the Methodist Episcopal Missionary Institute at Bremen, Germany (1860-66). He was acting president of the Boston University School of Theology (1866-73), and was president of Boston University (1873-1903), and dean of the School of Theology (1903-11), and after 1873 he was also professor of comparative theology and philosophy of religion. He published:

• The True Key of Ancient Cosmology (1882)
• Paradise Found—the Cradle of the Human Race at the North Pole (1885)
• The Quest of the Perfect Religion (1886)
• In the Footsteps of Arminius (1888)
• The Story of Gottlieb (1890)
• Religions of the World and the World Religion (1900)
• The Earliest Cosmologies (1909)
• The Universe as Pictured in Milton's Paradise Lost (1915)

When Boston University was chartered in 1869, he helped make it the first university in the country fully open to women. He also helped create Wellesley College in 1870. He was the brother of Henry White Warren.