Conrad Yeatis "Sonny" Clark was born July 21, 1931, in Herminie, Pennsylvania, a coal mining town southeast of Pittsburgh. His parents had come north from Stone Mountain, Georgia; his father, a miner named Emery Clark, died of a lung disease two weeks after Sonny was born, leaving Sonny the youngest of eight children. At twelve he moved with his family to Pittsburgh, where he continued the piano studies he had already begun.

At twenty, while visiting an aunt in California, Clark decided to stay on the West Coast and began working with saxophonist Wardell Gray. He traveled to San Francisco with bassist Oscar Pettiford, and within a couple of months was working with clarinetist Buddy DeFranco, joining DeFranco's quartet in 1953 and touring the United States and Europe with the group until January 1956 (documented on a run of DeFranco's Verve albums, including In a Mellow Mood, Cooking the Blues, and Autumn Leaves). During this period, on January 15, 1954, Clark also cut a trio and solo piano session with bassist Simon Brehm and drummer Bobby White, later issued as The Sonny Clark Memorial Album. In January 1956 he joined bassist Howard Rumsey's Lighthouse All-Stars, and on January 13, 1955, a working trio led by Clark himself was captured live at the Mocambo Club in Oakland, California, released decades later as Oakland, 1955. Wanting to relocate to the East Coast, Clark took a job accompanying singer Dinah Washington in February 1957, using the tour to move to New York City.

In New York, Clark quickly became one of the most in-demand pianists on the scene, prized for his rhythmic comping and clean, hard-swinging touch. He became a de facto house pianist for Blue Note Records under producer Alfred Lion, recording extensively as a sideman for the label alongside Kenny Burrell, Donald Byrd, Paul Chambers, John Coltrane, Dexter Gordon, Art Farmer, Curtis Fuller, Grant Green, Philly Joe Jones, Clifford Jordan, Jackie McLean, Hank Mobley, Art Taylor, and Wilbur Ware, among many others, while also turning up on dates led by Charles Mingus, Sonny Rollins, Billie Holiday, Stanley Turrentine, and Lee Morgan.

Clark's own run as a Blue Note leader began in mid-1957 and produced a remarkable string of sessions in barely six months: Dial "S" for Sonny (recorded July 21, 1957, his 26th birthday), Sonny's Crib (September 1, 1957, with a young John Coltrane in the sextet), and Sonny Clark Trio (October 13, 1957). A quintet date on January 5, 1958, with Art Farmer and Jackie McLean yielded Cool Struttin', the album most identified with him today and, alongside a companion date from December 1957, later reissued as Sonny Clark Quintets. Additional trio material recorded across late 1958 (issued decades afterward as Blues in the Night and The Art of the Trio) and a quintet session from March 1959 with Donald Byrd and Hank Mobley (eventually issued as My Conception) sat unreleased in Blue Note's vault for years, only reaching listeners in Japan in the late 1970s and the United States even later.

Clark kept working steadily as a sideman into the early 1960s, appearing on further sessions for Jackie McLean, Grant Green, Dexter Gordon, Ike Quebec, Don Wilkerson, and Stanley Turrentine, among others. On March 23, 1960, he cut a one-off trio date for Time Records with bassist George Duvivier and drummer Max Roach, released as Sonny Clark Trio (reissued in the 2010s as The 1960 Time Sessions). His final album as a leader, Leapin' and Lopin', was recorded November 13, 1961, with trumpeter Tommy Turrentine, tenor saxophonist Charlie Rouse, bassist Butch Warren, drummer Billy Higgins, and a guest appearance from Ike Quebec.

Clark struggled with heroin addiction for much of his adult life, and his health declined sharply in his final months. He passed away in New York City on January 13, 1963, at age 31; his death was officially attributed to a heart attack, though multiple biographers, including Sam Stephenson writing in The Paris Review, have concluded the underlying cause was a heroin overdose. His friend and fellow pianist Bill Evans dedicated the composition "N.Y.C.'s No Lark," an anagram of his name, to him on the 1963 album Conversations with Myself. In 1985, John Zorn, Wayne Horvitz, Ray Drummond, and Bobby Previte recorded an album of Clark's compositions as the Sonny Clark Memorial Quartet, titled Voodoo after one of his tunes, and Zorn revisited Clark's music again with Bill Frisell and George E. Lewis on News for Lulu (1988) and More News for Lulu (1992).

Clark's playing grew out of Bud Powell's bebop vocabulary but carried its own dark, blues-soaked harmonic sensibility and an unusually propulsive rhythmic drive, qualities AllMusic biographer Thom Jurek has called the quintessence of hard bop piano. He was, by wide consensus among the musicians who hired him, one of the most reliable and swinging accompanists in New York during the late 1950s, which is why Alfred Lion used him on so many Blue Note dates as both leader and sideman. As a composer he left behind a small but distinctive book of originals, "Cool Struttin'," "Sonny's Crib," and "Voodoo" chief among them, several of which were revived decades later by John Zorn's Sonny Clark Memorial Quartet and remain part of the working repertoire of hard bop pianists.