William Stanley Merwin (September 30, 1927 - March 15, 2019) is an American poet, credited with over 30 books of poetry, translation and prose. Born in New York City, Merwin grew up in Union City, New Jersey and Scranton, Pennsylvania. He attended Princeton University. In 1952, Merwin's first book of poetry, A Mask for Janus, was published in the Yale Younger Poets Series.

Merwin's early subjects were frequently tied to mythological or legendary themes, while many of his poems featured animals. A volume called The Drunk in the Furnace (1960) marked a change for Merwin, in that he began to write in a much more autobiographical way. In the 1960s, Merwin lived in a small apartment in New York City's Greenwich Village, and began to experiment boldly with metrical irregularity. His poems became much less tidy and controlled. He played with the forms of indirect narration typical of this period, a self-conscious experimentation explained in an essay called 'On Open Form' (1969). The Lice (1967) and The Carrier of Ladders (1970) remain his most influential volumes. These poems often used legendary subjects (as in 'The Hydra' or 'The Judgment of Paris') to explore highly personal themes.

In Merwin's later volumes — such as The Compass Flower (1977), Opening the Hand (1983), and The Rain in the Trees (1988) — one sees him transforming earlier themes in fresh ways, developing an almost Zen-like indirection. His latest poems are densely imagistic, dream-like, and full of praise for the natural world. He has lived in Hawaii since the 1970s, and one sees the influence of this tropical landscape everywhere in the recent poems, though the landscape remains emblematic and personal. Migration (2005) won the 2005 National Book Award for poetry. The Shadow of Sirius (2008) was awarded the 2009 Pulitzer Prize for poetry.

Besides being a prolific poet, he is also a respected translator of Spanish, French, Latin and Italian poetry (including Dante's Purgatorio) as well as poetry from Sanskrit, Yiddish, Middle English, Japanese and Quechua. In June 2010, the Library of Congress named Merwin the seventeenth United States Poet Laureate.

Among Merwin's correspndents were: Ellen Borden Stevenson (1907-1972), a Chicago patron of the arts and ex-wife of Illinois governor Adlai Stevenson; Mona Van Duyn, an American poet who taught at Washington University; and Graham Ackroyd, an English poet and artist.