Jack Spicer (January 30, 1925 – August 17, 1965) was an American poet often identified with the San Francisco Renaissance. In 2009, My Vocabulary Did This to Me: The Collected Poetry of Jack Spicer won the American Book Award for poetry. He spent most of his writing life in San Francisco.

Jack was born John Lester Spicer on January 30, 1925 in Los Angeles, the elder child of parents Dorothy Clause and John Lovely Spicer.

He graduated from Fairfax High School in 1942, and attended the University of Redlands from 1943 to 1945. While attending the University of Redlands, he befriended Warren Christopher. After graduation he lived in Los Angeles briefly, and worked as a movie extra and a private investigator.

Spicer ended up in Berkeley, and lived in a boarding house alongside Philip K. Dick. He spent the years 1945 to 1950; and from 1952 to 1955 at the University of California, Berkeley, where he began writing, doing work as a research linguist, and publishing some poetry (though he disdained publishing). In 1950, he refused to sign a "loyalty oath" during a time of McCarthyism.

During this time he searched out fellow poets, but it was through his alliances with Robert Duncan and Robin Blaser that Spicer forged a new kind of poetry, and together they referred to their common work as the Berkeley Renaissance. The three, who were all gay, also educated younger poets in their circle about their "queer genealogy": Rimbaud, Lorca, and other gay writers. Spicer's poetry of this period is collected in One Night Stand and Other Poems (1980). His Imaginary Elegies, later collected in Donald Allen's The New American Poetry 1945–1960 anthology, were written around this time.

In 1954, he co-founded the Six Gallery in San Francisco, which soon became famous as the scene of the October 1955 Six Gallery reading that launched the West Coast Beat movement. In 1955, Spicer moved to New York City and then to Boston, where he worked for a time in the Rare Book Room of Boston Public Library. Blaser was also in Boston at this time, and the pair made contact with a number of local poets, including John Wieners, Stephen Jonas, and Joe Dunn.

Spicer returned to San Francisco in 1956 and started working on After Lorca. This book represented a major change in direction for two reasons. Firstly, he came to the conclusion that stand-alone poems (which Spicer referred to as his one-night stands) were unsatisfactory and that henceforth he would compose serial poems. In fact, he wrote to Blaser that 'all my stuff from the past (except the Elegies and Troilus) looks foul to me.' Secondly, in writing After Lorca, he began to practice what he called "poetry as dictation". His interest in the work of Federico García Lorca, especially as it involved the cante jondo ideal, also brought him near the poetics of the deep image group. The Troilus referred to was Spicer's then unpublished play of that name. The play finally appeared in print in 2004, edited by Aaron Kunin, in issue 3 of No – A Journal of the Arts.

In 1957, Spicer ran a workshop called Poetry as Magic at San Francisco State College, which was attended by Duncan, Helen Adam, James Broughton, Joe Dunn, Jack Gilbert, and George Stanley. He also participated in, and sometimes hosted, Blabbermouth Night at a literary bar called The Place. This was a kind of contest of improvised poetry and encouraged Spicer's view of poetry as being dictated to the poet.