His family announced his death on Facebook, saying the cause was complications from the coronavirus.
Konitz came of musical age during the bebop movement, which revolutionized jazz in the 1940s with its fast-paced rhythmic drive and harmonic innovations, pioneered by the trailblazing saxophonist Charlie Parker.
Instead of imitating Parker's restless, high-speed cascades of sound, Konitz went in a different musical direction, developing improvised solos that seemed to float like clouds, structured not as bursts of sound but as well-wrought musical sculptures.
In the 1940s, he began to study and perform with pianist Lennie Tristano, who sought to blend elements of classical music with jazz, with polytonal chords and changing time signatures and harmonies.
Applying that approach to the saxophone, Konitz was one of the key musicians, along with Davis and baritone saxophonist Gerry Mulligan and others, who recorded "Birth of the Cool" in 1949 and 1950. Issued in 1957, the album is considered a landmark. Konitz's lyrical solos on several tunes, including "Moon Dreams," "Israel" and "Move," helping define a restrained, "cool" style of jazz, personified by Davis, Mulligan, Dave Brubeck, Paul Desmond and others.
In the words of the authoritative "New Grove Dictionary of Jazz," Konitz was "the foremost saxophonist in the cool style of jazz, and one of the few alto saxophonists of his generation to create a viable jazz style outside the dominating influence of Charlie Parker."
Konitz wrote a number of tunes, often punning on his name - "Subconscious-Lee," "Lone-Lee," "Leewise" - but he was perhaps better known for adapting standard tunes to his meticulous, searching style of improvisation. He was a deep admirer of the music of Frank Sinatra and returned over and over to such familiar works as "All the Things You Are" and "Body and Soul," finding fresh prisms of musical light in each encounter.
"I like to play very familiar tunes and then try to stretch them as far as they'll go," he told Marian McPartland in 1992 on her NPR show "Piano Jazz."
After working with Tristano, Davis and saxophonist Warne Marsh in his early days, Konitz fell out of favor in the 1960s, even as the experimental jazz movement that he helped launch began to gain a foothold.
He found greater acceptance in Europe for many years before gaining increased acclaim as a jazz elder whose authority and musical remained undiminished, even in his 90s. Instead of leading an established group, he often performed in duos or small ensembles with other forward-looking musicians, including bassist Charlie Haden, guitarists John Scofield and Bill Frisell and pianists Kenny Barron and Brad Mehldau.
He was honored as a Jazz Master by the National Endowment for the Arts in 2009.