John Simmons Barth (; May 27, 1930 – April 2, 2024) was an American writer best known for his postmodern and metafictional fiction. His most highly regarded and influential works were published in the 1960s, and include The Sot-Weed Factor, a whimsical retelling of Maryland's colonial history; Giles Goat-Boy, a satirical fantasy in which a university is a microcosm of the Cold War world; and Lost in the Funhouse, a self-referential and experimental collection of short stories. He was co-recipient of the National Book Award in 1973 for his episodic novel Chimera.

Barth was born in Cambridge, Maryland, and briefly studied "Elementary Theory and Advanced Orchestration" at Juilliard before attending Johns Hopkins University, receiving a B.A. in 1951 and an M.A. in 1952 (for which he wrote a thesis novel, The Shirt of Nessus). He was a professor at Penn State University (1953-1965), SUNY Buffalo (1965-1973), Boston University (visiting professor, 1972-1973), and Johns Hopkins University (1973-1995) before he retired in 1995.