Lester Willis Young was born August 27, 1909, in Woodville, Mississippi, to Willis Handy Young, a schoolteacher and bandmaster from Thibodaux, Louisiana, and Lizetta Johnson Young, a piano teacher from Woodville. The family settled in New Orleans's Algiers neighborhood, and by his teens Lester was touring with the Young Family Band, a carnival and vaudeville outfit his father drilled on drums, violin, and multiple reeds. In 1919 the family relocated to Minneapolis, where Young switched to tenor saxophone, absorbing the melodic economy of Louis Armstrong and, decisively, the light, floating tone of white C-melody saxophonist Frankie Trumbauer, whose 1927 solo on "Singin' the Blues" (with cornetist Bix Beiderbecke) Young later named as a formative model. In 1927, at eighteen, he left the family band rather than tour the segregated Deep South again, striking out on his own through Midwestern territory bands.

By 1932 Young had joined bassist Walter Page's Original Blue Devils in Oklahoma City, and by 1933 he had settled in Kansas City, working with Bennie Moten's band before joining pianist Count Basie's Kansas City outfit. He left Basie briefly in 1934 for a disastrous stint replacing Coleman Hawkins in Fletcher Henderson's New York orchestra, whose musicians, accustomed to Hawkins's dense, heavy-vibrato attack, gave Young's lighter approach a cold reception; he also passed briefly through Andy Kirk's Clouds of Joy before returning to Basie for good by 1936. His first recordings came that year under the pseudonymous billing "Jones-Smith, Incorporated" (Vocalion 3441, cut in Chicago; sources differ on whether the date was October 9 or November 9, 1936), a workaround for Basie's existing Decca contract. "Shoe Shine Boy" and "Oh, Lady Be Good" from that session made Young's floating, understated tenor sound an overnight sensation among musicians.

Through the Basie band's rise to national prominence from 1937 to 1940, Young became half of one of jazz's most storied internal rivalries: his cool, horizontal phrasing set against tenor sectionmate Herschel Evans's harder-driving, Hawkins-influenced sound, a contrast fans and bandmates treated as a running contest until Evans's death from a heart ailment in February 1939. Young's Basie-era features, cut for Decca, Vocalion, and Okeh, include "One O'Clock Jump" (1937) and, on the small-group Kansas City Seven session credited separately from the full orchestra, "Lester Leaps In" (Vocalion, recorded September 5, 1939). He was equally prolific in Basie-adjacent small-group dates: the Kansas City Six, recorded for Milt Gabler's Commodore label in New York in September 1938 (sources again disagree on the exact date, September 8 versus September 27), found Young switching to clarinet on several sides, including a widely noted solo on "I Want a Little Girl." It was also during these Basie years that Young formed his close friendship with Billie Holiday (no profile yet exists for her on JazzProfiles.com), whom he had met at a Harlem jam session in the early 1930s; the two toured together, and Young lived for a time in the apartment Holiday shared with her mother. Young began calling her "Lady Day," and Holiday, who considered Franklin D. Roosevelt the greatest man in the country, decided Young deserved an equivalent title and started calling him "Pres" (short for President), a name shortened by fellow musicians to "Prez." The two also recorded together extensively in small groups led on paper by pianist Teddy Wilson for Brunswick and Vocalion between 1937 and 1938, sessions now anthologized across Columbia's Quintessential Billie Holiday reissue series, on which Young's obbligato lines behind Holiday's vocals are counted among the most sympathetic instrumental accompaniment in jazz.

Young left the Basie band in December 1940, for reasons biographers still dispute (a superstitious refusal to play a gig falling on Friday the 13th versus a departure planned for months), and spent the early 1940s leading small groups on the West Coast, often alongside his drummer brother Lee Young and, from 1942, a young pianist named Jimmy Rowles. On July 15, 1942, in Los Angeles, Young cut a trio session for the small Philo label with pianist Nat "King" Cole (billed under a pseudonym for contractual reasons) and bassist Red Callender, supervised by a young promoter named Norman Granz; commercially unreleased at the time, the four sides ("Tea for Two," "I Can't Get Started," and others) finally appeared on Philo in 1945 and became one of the most prized items in Young's catalog. He returned to Basie for a ten-month stint beginning December 1943, recording small-group sides for Harry Lim's Keynote label ("These Foolish Things," "Just You, Just Me") along the way.

Young was inducted into the U.S. Army in September 1944 while touring with Basie in Los Angeles. Unlike white bandleaders such as Glenn Miller and Artie Shaw, who were assigned to service bands, Young was placed in the regular infantry with no opportunity to play his horn. Stationed at Fort McClellan, Alabama, he was found with marijuana and alcohol among his possessions, court-martialed, and did not contest the charges. He served roughly a year in an army detention barracks before receiving a dishonorable discharge in late 1945, an experience biographers regard as a lasting psychological wound; Young later commemorated it in the tune "D.B. Blues." From 1946 he joined Norman Granz's touring Jazz at the Philharmonic troupe, a fixture of his work for the next decade, and recorded steadily for Aladdin (1945-1947), Savoy (1944, 1949-1950), and, from the early 1950s on, almost exclusively for Granz's Norgran, Clef, and Verve labels. Landmark dates from this period include Lester Young with the Oscar Peterson Trio (recorded 1952) and, after a November 1955 hospitalization for a nervous breakdown, a run of acclaimed reunion sessions in January 1956: The Jazz Giants '56 (January 12, with Roy Eldridge, Teddy Wilson, Vic Dickenson, Freddie Green, Gene Ramey, and Jo Jones) and Pres and Teddy (January 13, reuniting Young with Teddy Wilson). Pres and Sweets, a quintet date with trumpeter Harry "Sweets" Edison backed by Oscar Peterson, Herb Ellis, Ray Brown, and Buddy Rich, followed in November 1955.

On December 8, 1957, Young appeared on the live CBS broadcast The Sound of Jazz, reuniting on camera with Billie Holiday for a rendition of her "Fine and Mellow" alongside Coleman Hawkins, Ben Webster, Roy Eldridge, and Gerry Mulligan; critic Nat Hentoff, present in the control room, later wrote that Young's solo reduced the crew to tears, and the performance is widely regarded as one of the most emotionally direct moments ever captured on television. Young toured Europe with Miles Davis and the Modern Jazz Quartet in 1956, but his health, undermined by years of heavy drinking and poor eating, continued to deteriorate. In March 1959 he traveled to Paris for an engagement at the Blue Note club with a rhythm section led by drummer Kenny Clarke, recording his final studio session there on March 2 (issued as Lester Young in Paris, Verve MG V-8378, 1960). Exhausted and drinking heavily on almost no food, he suffered severe internal bleeding on the flight back to New York and died in his hotel room in the early hours of March 15, 1959, at age 49. Holiday, from whom he had been estranged for several years, attended his funeral and reportedly told a companion she would be the next to go; she died four months later, on July 17, 1959.

Young's tenor sound was a direct rebuke to the instrument's dominant model in the 1920s and early 1930s, the thick-toned, heavily vibratoed, harmonically aggressive style of Coleman Hawkins. Drawing instead on the light, airy phrasing of C-melody saxophonist Frankie Trumbauer, Young played with a soft attack, minimal vibrato, and a way of floating just behind or across the beat rather than driving hard through it, giving his lines a horizontal, melodic quality where Hawkins's were vertical and chordal. He was also an accomplished clarinetist, heard to striking effect on the 1938 Kansas City Six sides. Young's rhythmic freedom and harmonic curiosity anticipated bebop by nearly a decade and were an acknowledged influence on John Coltrane and, more directly, on Charlie Parker's own rhythmic conception. His most direct legacy, though, is the entire postwar "cool" tenor lineage: when Woody Herman assembled the reed section for his Second Herd in 1947, arranger Jimmy Giuffre built "Four Brothers" explicitly around players who had absorbed Young's sound wholesale, Zoot Sims, Stan Getz, Herbie Steward, and baritone saxophonist Serge Chaloff (soon joined by fellow Young disciple Al Cohn), a section sound that in turn shaped Gerry Mulligan, Warne Marsh, and Paul Desmond. Beyond music, Young is widely credited with helping popularize "cool" as a term of approval and pieces of the era's hipster slang more broadly (he used "bread" for money), and his taciturn, wordplay-filled speech and his signature flat-brimmed porkpie hat became inseparable from his image; Charles Mingus's 1959 elegy "Goodbye Pork Pie Hat" (later retitled "Theme for Lester Young") and Wayne Shorter's "Lester Left Town" are among the direct musical tributes his death prompted.