Joseph John Campbell (March 26, 1904 – October 30, 1987) was an American writer. He was a professor of literature at Sarah Lawrence College who worked in comparative mythology and comparative religion. His work covers many aspects of the human condition. Campbell's best-known work is his book The Hero with a Thousand Faces (1949), in which he discusses his theory of the journey of the archetypal hero shared by world mythologies, termed the monomyth.

Since the publication of The Hero with a Thousand Faces, Campbell's theories have been applied by a wide variety of modern writers and artists. His philosophy has been summarized by his own often repeated phrase: "Follow your bliss." He gained recognition in Hollywood when George Lucas credited Campbell's work as influencing his Star Wars saga.

Joseph Campbell was born in White Plains, New York, on March 26, 1904, the elder son of hosiery importer and wholesaler Charles William Campbell, from Waltham, Massachusetts, and Josephine (née Lynch), from New York. Campbell was raised in an upper-middle-class Irish Catholic family; he related that his paternal grandfather Charles had been "a peasant" who came to Boston from County Mayo in Ireland, and became the gardener and caretaker at the Lyman Estate at Waltham, where his son Charles William Campbell grew up and became a successful salesman at a department store prior to establishing his hosiery business. During his childhood, he moved with his family to New Rochelle, New York. In 1919, a fire destroyed the family home in New Rochelle, killing his maternal grandmother and injuring his father, who tried to save her.

In 1921, Campbell graduated from the Canterbury School in New Milford, Connecticut. While at Dartmouth College he studied biology and mathematics, but decided that he preferred the humanities. He transferred to Columbia University, where he received a Bachelor of Arts degree in English literature in 1925 and a Master of Arts degree in medieval literature in 1927. At Dartmouth he had joined Delta Tau Delta. An accomplished athlete, he received awards in track and field events, and, for a time, was among the fastest half-mile runners in the world.

In 1924, Campbell traveled to Europe with his family. On the ship during his return trip he encountered the messiah elect of the Theosophical Society, Jiddu Krishnamurti; they discussed Indian philosophy, sparking in Campbell an interest in Hindu and Indian thought. In 1927, he received a fellowship from Columbia University to study in Europe. Campbell studied Old French, Provençal, and Sanskrit at the University of Paris and the University of Munich. He learned to read and speak French and German.

On his return to Columbia University in 1929, Campbell expressed a desire to pursue the study of Sanskrit and modern art in addition to medieval literature. Lacking faculty approval, Campbell withdrew from graduate studies. Later in life he jested that it is a sign of incompetence to have a PhD in the liberal arts, the discipline covering his work.

With the arrival of the Great Depression, Campbell spent the next five years (1929–1934) living in a rented shack in Woodstock, New York. There, he contemplated the next course of his life while engaged in intensive and rigorous independent study. He later said that he "would divide the day into four three-hour periods, of which I would be reading in three of the three-hour periods, and free one of them ... I would get nine hours of sheer reading done a day. And this went on for five years straight."

Campbell traveled to California for a year (1931–1932), continuing his independent studies and becoming a close friend of the budding writer John Steinbeck and his wife Carol. Campbell had met Carol's sister, Idell, on a Honolulu cruise and she introduced him to the Steinbecks. Campbell had an affair with Carol. On the Monterey Peninsula, Campbell, like John Steinbeck, fell under the spell of the marine biologist Ed Ricketts (the model for "Doc" in Steinbeck's novel Cannery Row as well as central characters in several other novels). Campbell lived for a while next door to Ricketts, participated in professional and social activities at his neighbor's, and accompanied him, along with Xenia and Sasha Kashevaroff, on a 1932 journey to Juneau, Alaska on the Grampus. Campbell began writing a novel centered on Ricketts as a hero but, unlike Steinbeck, did not complete his book.