John Arthur "Jaki" Byard (; June 15, 1922 – February 11, 1999) was an American jazz multi-instrumentalist, composer, and arranger. Mainly a pianist, he also played tenor and alto saxophones, among several other instruments. He was known for his eclectic style, incorporating everything from ragtime and stride to free jazz.

Byard played with trumpeter Maynard Ferguson in the late 1950s and early 1960s, and was a member of bands led by bassist Charles Mingus for several years, including on several studio and concert recordings. The first of his recordings as a leader was in 1960, but, despite being praised by critics, his albums and performances did not gain him much wider attention. In his 60-year career, Byard recorded at least 35 albums as leader, and more than 50 as a sideman. Byard's influence on the music comes from his combining of musical styles during performance, and his parallel career in teaching.

From 1969 Byard was heavily involved in jazz education: he began teaching at the New England Conservatory of Music and went on to work at several other music institutions, as well as having private students. He continued performing and recording, mainly in solo and small group settings, but he also led two big bands – one made up of some of his students, and the other of professional musicians. His death, from a single gunshot while in his home, remains an unsolved mystery.