William John Evans was born August 16, 1929, in Plainfield, New Jersey, to Harry Evans, a golf course operator of Welsh descent, and Mary Evans (née Soroka), of Carpatho-Rusyn ancestry. He began piano lessons at six with a local teacher, Helen Leland, adding violin at seven and later flute and piccolo, and by his teens was playing paid dance and wedding gigs around New Jersey alongside his older brother Harry, a fellow musician two years his senior to whom he stayed close his whole life. After graduating North Plainfield High School in 1946, Evans studied at Southeastern Louisiana College, earning a Bachelor of Music in piano performance and a second bachelor's degree in music education by 1950. He served three years in the U.S. Army, 1951 to 1954, playing flute, piccolo, and piano in the Fifth Army Band at Fort Sheridan, Illinois, then settled in New York and took a three-semester postgraduate composition course at the Mannes College of Music in 1955.

Evans's earliest significant recordings as a sideman came with clarinetist Tony Scott's groups and on a session led by theorist and composer George Russell, whose 1956 album The Jazz Workshop (RCA Victor) gave Evans an early showcase for the kind of harmonically advanced writing that suited him. His own leader debut, New Jazz Conceptions (Riverside RLP 12-223), was recorded in 1956 with bassist Teddy Kotick and drummer Paul Motian and released in February 1957; it sold modestly but included the first recording of Evans's original "Waltz for Debby," written for his young niece. A second Riverside trio date, Everybody Digs Bill Evans (RLP 12-291, recorded December 1958, released 1959) with bassist Sam Jones and drummer Philly Joe Jones, carried a striking endorsement on its cover: handwritten praise from Miles Davis, Cannonball Adderley, and Ahmad Jamal.

Davis brought Evans into his sextet in April 1958, alongside Cannonball Adderley, John Coltrane, Paul Chambers, and Jimmy Cobb, replacing Red Garland; Evans left that November, worn down by life on the road and by his father's declining health, and was replaced by Wynton Kelly. Davis brought him back into the studio in early 1959 specifically to record Kind of Blue, built around the modal, scale-based writing Evans and Davis had been discussing, and Evans plays on four of the album's five tracks (Kelly takes "Freddie Freeloader"); Evans also co-wrote "Blue in Green," a credit Davis initially withheld and only later acknowledged. Released in August 1959, Kind of Blue went on to become the best-selling jazz album in history.

In mid-1959, Evans formed a trio with bassist Scott LaFaro and Paul Motian that reimagined what a piano trio could do: rather than the bass and drums simply keeping time under a soloing pianist, all three musicians improvised in constant, equal conversation. The trio recorded Portrait in Jazz in December 1959 and Explorations in February 1961, both for Riverside, and on June 25, 1961, recorded a full day of sets at the Village Vanguard in New York that yielded two landmark live albums, Sunday at the Village Vanguard and Waltz for Debby. Ten days later, on July 6, 1961, LaFaro was killed in a car accident in upstate New York at age twenty-five. Evans was devastated and did not perform in public again for several months. When he returned to the studio, bassist Chuck Israels took the chair, and Evans kept a working trio, its personnel and instrumentation the near-constant thread of his career, for the rest of his life. Other significant recordings from these years include the trio session Moon Beams and the sideman date Interplay (both 1962, Riverside) with trumpeter Freddie Hubbard and guitarist Jim Hall, plus a pair of piano-and-guitar duo albums with Hall, Undercurrent (1962, United Artists) and Intermodulation (1966, Verve).

Evans signed with Verve in 1962, where producer Creed Taylor and later Helen Keane (who managed and produced him for the rest of his life) documented a prolific decade: the overdubbed solo-piano record Conversations with Myself (1963), which won Evans his first Grammy Award; Trio '64 with bassist Gary Peacock and Motian; and, after Chuck Israels departed in 1966, an eleven-year partnership with bassist Eddie Gómez, the longest of any Evans bassist, across a rotating cast of drummers: Jack DeJohnette (1967-68), Marty Morell (1968-74), and Eliot Zigmund (1975-78). Bill Evans at the Montreux Jazz Festival (1968), with Gómez and DeJohnette, and the solo album Alone (1970) each won Evans a second and third Grammy. Moving to Columbia, The Bill Evans Album (1971), featuring Evans on both acoustic and electric piano, won two Grammy Awards at the 1972 ceremony, and Living Time (1972) paired him with George Russell's big-band writing in a more experimental, suite-length format. A move to Fantasy in the mid-1970s produced the duo album Intuition (1975) with Gómez, the trio record Since We Met (1976), the all-star sextet date Quintessence (1977) with saxophonist Harold Land and guitarist Kenny Burrell, and I Will Say Goodbye (1977), which brought Evans a fourth Grammy.

Evans's brother Harry, who had struggled with schizophrenia, died by suicide in the spring of 1979; friends and biographers have long described that loss as devastating to Evans and a contributing factor to his own accelerating decline. His final working trio, formed in 1978 with bassist Marc Johnson and drummer Joe LaBarbera, recorded two more Grammy-winning albums for Warner Bros., Affinity (1979, with harmonica player Toots Thielemans) and We Will Meet Again (recorded August 1979, featuring trumpeter Tom Harrell and dedicated to Harry's memory), plus the posthumously released You Must Believe in Spring (recorded 1977, issued 1981). Evans had struggled with heroin addiction since the late 1950s, worsened by LaFaro's death, and later with cocaine; chronic hepatitis, untreated for years, combined with a bleeding ulcer and cirrhosis to end his life on September 15, 1980, at Mount Sinai Hospital in New York City. He was 51. Evans won seven Grammy Awards from thirty-one nominations over his career, two of them posthumous, and was inducted into the Down Beat Hall of Fame.

Evans's playing was defined by an introspective, classically inflected touch, a harmonic vocabulary drawn from Debussy and Ravel as much as from jazz forebears, and a conception of the piano trio as three equal, conversing voices rather than a soloist over accompaniment, a model he and Scott LaFaro pioneered together and that reshaped how the format was played for generations after. His voicings, often built from rootless left-hand chords that implied harmony rather than stating it outright, and his behind-the-beat, "singing" melodic phrasing became so widely emulated that critics speak of a "school" of Evans-influenced pianists. He named Bud Powell as his single greatest influence, and in turn shaped the playing of Herbie Hancock, Chick Corea, Keith Jarrett, and Brad Mehldau, among many others; Miles Davis himself called Evans's touch on the keyboard "like crystal notes" falling from a waterfall.