William John Evans (August 16, 1929 – September 15, 1980) was an American jazz pianist and composer who worked primarily as the leader of his trio. His extensive use of impressionist harmony, block chords, innovative chord voicings, and trademark rhythmically independent "singing" melodic lines continue to influence jazz pianists today.

Born in Plainfield, New Jersey, Evans studied classical music at Southeastern Louisiana College and the Mannes School of Music, in New York City, where he majored in composition and received an artist diploma. In 1955, he moved to New York City, where he worked with bandleader and theorist George Russell. In 1958, Evans joined Miles Davis's sextet, which in 1959, then immersed in modal jazz, recorded Kind of Blue, the best-selling jazz album of all time.

In late 1959, Evans left Davis's band and began his career as a leader, forming a trio with bassist Scott LaFaro and drummer Paul Motian, a group now regarded as a seminal modern jazz trio. They recorded two studio albums, Portrait in Jazz and Explorations, and two albums recorded during a 1961 engagement at New York's Village Vanguard jazz club: Sunday at the Village Vanguard and Waltz for Debby. A complete set (on three CDs) of their Vanguard recordings was issued decades later. Ten days after this booking ended, LaFaro died in a car crash. After months without public performances, Evans reemerged with a new trio featuring Chuck Israels on bass. In 1963, Evans recorded the Grammy Award–winning Conversations with Myself, a solo album produced with overdubbing technology. In 1966, he met bassist Eddie Gómez, with whom he worked for the next 11 years. In the mid-1970s, Evans collaborated with the singer Tony Bennett on two critically acclaimed albums: The Tony Bennett/Bill Evans Album (1975) and Together Again (1977).

Many of Evans's compositions, such as "Waltz for Debby" and "Time Remembered", have become standards, played and recorded by many artists. Evans received 31 Grammy nominations and seven awards, and was inducted into the DownBeat Jazz Hall of Fame.