Thelonious Sphere Monk was born October 10, 1917, in Rocky Mount, North Carolina, to Thelonious and Barbara Monk. The family moved to New York City around 1922, settling in the San Juan Hill neighborhood of Manhattan. Monk briefly tried trumpet before switching to piano around age nine, learning stride technique from a neighbor, Alberta Simmons, while his mother had him accompany hymns at church. He later studied classical piano for two years under an Austrian-born teacher, Simon Wolf, working through Bach, Mozart, Beethoven, and Chopin, and attended Stuyvesant High School in Manhattan without graduating. By sixteen he had toured briefly as an accompanist for a traveling evangelist, and in the late 1930s he found steady work as house pianist at Minton's Playhouse in Harlem.

At Minton's, Monk took part nightly in the after-hours cutting sessions that, alongside Dizzy Gillespie, Charlie Christian, Kenny Clarke, Charlie Parker, and a young Miles Davis, forged the harmonic and rhythmic vocabulary of bebop. He failed his 1943 Army induction physical, classified psychiatrically unfit, and stayed in New York. His first commercial recordings came in 1944 as a sideman with the Coleman Hawkins Quartet. Through saxophonist Ike Quebec he met Blue Note Records co-founder Alfred Lion, and beginning in 1947 Monk cut a series of leader sessions for the label with a rotating cast that included Milt Jackson, Art Blakey, Sahib Shihab, and Idrees Sulieman; these were later gathered as Genius of Modern Music, Vol. 1 and Vol. 2. In August 1951, New York police searched a parked car occupied by Monk and pianist Bud Powell and found narcotics; Monk refused to identify the drugs as Powell's, and the resulting conviction cost him his New York City cabaret card, barring him for roughly six years from performing in any venue serving liquor. He kept working through low-profile Brooklyn club dates and a 1952-54 contract with Prestige Records, and on Christmas Eve 1954 he was the pianist on Miles Davis's session for Bags' Groove at Rudy Van Gelder's Hackensack studio, an encounter later mythologized (not entirely accurately) as a heated clash over Monk's dense comping behind Davis's solos. That same year he traveled to Paris, recording solo piano for French radio and meeting Baroness Pannonica "Nica" de Koenigswarter, a Rothschild-family patron who became his lifelong friend and financial supporter.

Orrin Keepnews signed Monk to Riverside Records in 1955, pairing him first with safer commercial ground, an album of Duke Ellington compositions, before Brilliant Corners (recorded October-December 1956) became his first widely praised original statement, built around the title track's famously difficult, tempo-shifting theme with Max Roach on drums and timpani and Sonny Rollins and Ernie Henry on saxophones. His cabaret card restored in 1957, Monk opened a celebrated six-month residency at the Five Spot Café that June with a quartet featuring John Coltrane on tenor, Wilbur Ware on bass, and Shadow Wilson on drums, a pairing documented commercially only on the septet album Monk's Music (recorded June 1957 with Coltrane, Coleman Hawkins, Art Blakey, and Gigi Gryce) and later, more fully, on tapes issued posthumously as Thelonious Monk with John Coltrane. A second Five Spot residency in 1958 introduced tenor saxophonist Johnny Griffin, captured on Thelonious in Action and Misterioso. On February 28, 1959, Monk fronted a ten-piece orchestra at New York's Town Hall, playing arrangements of his own tunes that pianist and arranger Hall Overton built out with Monk's direct involvement; the band included trumpeter Donald Byrd, altoist Phil Woods, tenor saxophonist Charlie Rouse, and baritone saxophonist Pepper Adams, released as The Thelonious Monk Orchestra at Town Hall.

Rouse joined Monk's working quartet permanently that same year and stayed through 1970, the longest tenure of any Monk sideman, anchoring records including 5 by Monk by 5 (1959, with Thad Jones) and Monk's solo recital Thelonious Alone in San Francisco (1959). Monk signed with Columbia Records in 1962, and his label debut Monk's Dream (recorded and released 1963, with bassist John Ore and drummer Frankie Dunlop alongside Rouse) became the best-selling album of his lifetime. Columbia's publicity push culminated in a February 1964 Time magazine cover story, "The Loneliest Monk," making him one of only a handful of jazz musicians ever to receive that honor. He expanded the working quartet back into a Hall Overton-arranged big band for Big Band and Quartet in Concert, recorded live at Philharmonic Hall on December 30, 1963, with soprano saxophonist Steve Lacy in the section. A 1964 rhythm-section change brought in bassist Larry Gales and drummer Ben Riley, who stayed with Monk more than four years through albums including Criss-Cross (1963), It's Monk's Time (1964), the solo album Solo Monk (1965), Straight, No Chaser (1966-67), and Underground (1967-68), his final quartet studio album for the label.

Monk's public activity thinned steadily after 1968; his last quartet performance with Rouse, Gales, and Riley came at an October 1968 concert arranged by a Palo Alto, California teenager, unreleased until the 2020 album Palo Alto. In November 1971 he undertook a farewell world tour with the all-star Giants of Jazz, alongside Dizzy Gillespie, Art Blakey, Sonny Stitt, Kai Winding, and Al McKibbon, and made his final studio recordings that same month in London for producer Alan Bates's Black Lion label, issued as Something in Blue and The Man I Love. He performed only sporadically for the rest of the decade and stopped playing piano altogether around 1976, spending his last six years largely in seclusion at Nica de Koenigswarter's home in Weehawken, New Jersey. Thelonious Monk passed away there of a stroke on February 17, 1982, at age 64. He received a Grammy Lifetime Achievement Award in 1993 and a posthumous special Pulitzer Prize citation in 2006 for a body of work that transformed the harmonic and structural language of jazz.

Monk built his music from dissonance treated as consonance: flatted ninths and fifths, unresolved whole-tone runs, deliberately "wrong" clashing intervals, and a percussive, often halting attack punctuated by silence, all set against a left hand still rooted in the stride tradition of James P. Johnson and Duke Ellington, whom Monk cited as his deepest influence. He rarely played fast for its own sake, preferring space, repetition, and abrupt hesitations that made his soloing sound structurally inevitable rather than merely virtuosic; he was known to stand up mid-performance to dance beside the piano before returning to the keyboard. Critical reception ran from bewildered dismissal in the early 1950s (poet Philip Larkin memorably derided him as "the elephant on the keyboard") to, by the Riverside and Columbia years, recognition as one of jazz's essential composers; by some counts he is the second-most-recorded jazz composer in history after Ellington, and "'Round Midnight" is the single most-recorded jazz standard by one composer. Disciples ranging from Bud Powell's generation of boppers to dedicated later interpreters like soprano saxophonist Steve Lacy, who devoted much of a five-decade career to Monk's book, carried his compositional logic into new contexts long after his death.