William James Basie was born on August 21, 1904, in Red Bank, New Jersey, the son of Harvey Lee Basie, a coachman and later groundskeeper who played the mellophone, and Lillian (Childs) Basie, a laundress and pianist who paid 25 cents a lesson for her son's first piano instruction. He left junior high school and spent much of his time at Red Bank's Palace Theater, where chores earned him free admission and where he learned to improvise accompaniment for the acts and the silent films. He leaned toward drums until he heard Sonny Greer, a fellow Red Bank native who went on to play with Duke Ellington, and at fifteen he committed to piano. Around 1920 he moved to Harlem, where he fell in with the stride pianists Willie "the Lion" Smith and James P. Johnson, and Fats Waller, then playing organ for silent films at the Lincoln Theater, taught him the instrument that Basie later played professionally and on records.

He toured the Keith and TOBA vaudeville circuits as a soloist, accompanist and music director for blues singers, dancers and comedians, and in 1927 one of those troupes broke up in Kansas City, Missouri, where he stayed, working in a silent-movie house (and at the organ of the Eblon Theater). In July 1928 he joined Walter Page's Blue Devils, whose singer was Jimmy Rushing, and in 1929 he moved to the more polished Kansas City orchestra of Bennie Moten, where he was pianist and, with Eddie Durham, who put the music on paper, co-arranger. Basie claimed credit for the band's "Moten Swing," played four-hand and two-piano passages with Moten, and recorded with the band in Chicago. Moten died on April 2, 1935, after a failed tonsillectomy, and Basie put together a nine-piece band from the wreckage, billed as the Barons of Rhythm, with Page on bass, Jo Jones on drums, Lester Young on tenor saxophone and Rushing as vocalist. The group became the house band at the Reno Club, broadcast late at night on local radio, and an announcer on those broadcasts is the usual source of the "Count" title, bestowed to put him in the company of Ellington and Earl Hines. The producer John Hammond heard the broadcasts, went to Kansas City, and arranged a Chicago recording session in October 1936 at which four sides were cut for Vocalion under the name Jones-Smith Incorporated, the earliest records of Lester Young. By the end of 1936 the band had moved to Chicago's Grand Terrace Cafe, and its first session for Decca followed in January 1937.

The orchestra Basie led from 1935 until his death is a separate subject, covered in full in the Count Basie Orchestra profile, and only its outline belongs here. It reached New York in 1937 and had its first hit with "One O'Clock Jump" the same year; a long stand at the Famous Door in 1938 and a celebrated battle of the bands with Chick Webb at the Savoy made it a national attraction. Its rhythm section, with Page, Jones and, from 1937, guitarist Freddie Green, became a model for swing, and Basie often worked from head arrangements that the band built and memorized in rehearsal. He appeared with the band in five films released in 1943, saw the postwar decline of big bands force him to break up the orchestra at the end of the 1940s, and led small groups for the next couple of years before reorganizing a 16-piece band in 1952. That band, usually called the "New Testament" orchestra against the "Old Testament" band of the 1930s and 1940s, toured abroad from 1954, added the singer Joe Williams that year, and had its breakthrough with Count Basie Swings, Joe Williams Sings (1955), the single "April in Paris," and the 1957 album Basie, known as The Atomic Mr. Basie. At the first Grammy Awards ceremony Basie won two awards for that album, becoming the first African American to win a Grammy.

The man at the keyboard is easy to lose behind the band, and his small-group and duo work shows him most clearly. Even in the 1950s he made records apart from the orchestra: a sextet date for Clef recorded in 1952 and issued as The Swinging Count!, on which he plays organ throughout and piano on most tracks alongside Paul Quinichette, Joe Newman, Freddie Green and Buddy Rich; Count Basie Presents Eddie Davis Trio + Joe Newman (recorded December 1957), on which he is the pianist; and Memories Ad-Lib (recorded October 1958), organ accompaniment for Joe Williams. In July 1961 he joined Ellington for First Time! The Count Meets the Duke, with both orchestras and, on most selections, both pianists, and in March 1962 he recorded Count Basie and the Kansas City 7 for Impulse!, an octet date with Thad Jones, Frank Wess, Frank Foster, Eric Dixon, Freddie Green, Eddie Jones and Sonny Payne in which he plays piano and organ and which AllMusic's Scott Yanow rated the best of his few small-group sessions of the decade. Through the 1960s the orchestra was heard mostly with singers: Frank Sinatra (Sinatra-Basie in 1962, It Might as Well Be Swing in 1964, and the live Sinatra at the Sands in 1966), Ella Fitzgerald (Ella and Basie!, 1963), Sarah Vaughan, Billy Eckstine, Tony Bennett, Sammy Davis Jr. and Jackie Wilson.

After a series of short-term label affiliations Basie signed in the early 1970s with Pablo Records, founded by the producer Norman Granz, and recorded for it for the rest of his life, in settings far more varied than the big-band dates of the previous decade; Britannica notes that he concentrated on small-group and piano-duet recordings in these years. The Pablo run began with Loose Walk, a session with Roy Eldridge and Eddie "Lockjaw" Davis recorded in 1972 and released later, and Basie Jam (recorded December 1973), a jam session on which he plays organ and piano with Davis, Zoot Sims, J.J. Johnson and Harry Edison. Other Pablo dates: The Bosses (1973), with the blues shouter Big Joe Turner; For the First Time (1974), a piano trio with Ray Brown and drummer Louie Bellson, followed by For the Second Time (recorded August 28, 1975); and a series of dates with Oscar Peterson, beginning with Satch and Josh (recorded December 2, 1974, with Basie on piano and organ against Peterson's piano, backed by Freddie Green, Brown and Bellson) and continuing with Satch and Josh...Again (1977) and the February 1978 sessions that yielded Night Rider, Yessir, That's My Baby and The Timekeepers. Britannica singles out the Basie-Peterson albums for the contrast between Basie's economy and Peterson's dexterity. Basie & Zoot (recorded April 9, 1975, in New York, with Sims, bassist John Heard and Bellson) won the Grammy for best jazz performance by a soloist. The Kansas City series of small-group dates followed: Kansas City 5 (January 26, 1977, with Milt Jackson and Joe Pass), Kansas City 8: Get Together (September 4, 1979, with Clark Terry, Edison and bassist John Clayton), Kansas City 7 (April 10, 1980, with Freddie Hubbard and Johnson), Kansas City 6 (November 1, 1981) and Mostly Blues...and Some Others (June 22, 1983). Basie Jam 2 and Basie Jam 3, both drawn from a May 1976 session with Benny Carter, Clark Terry, Al Grey and Pass, round out the jam-session records. He also made The Gifted Ones (1977) with Dizzy Gillespie and took part in jam sessions at the Montreux Jazz Festival in 1975 and 1977.

Basie suffered a heart attack in 1976 that kept him off the stand for several months, was hospitalized again in 1981, and after that drove an electric wheelchair onto the stage. His wife Catherine, whom he had married in 1940 and with whom he had a daughter, Diane, died in 1983 at their home in Freeport in the Bahamas, where the couple had moved in the 1970s. He kept leading the orchestra until a month before his death, and 88 Basie Street, recorded in May 1983, released in 1984 and arranged by Sammy Nestico, brought his ninth and last Grammy. He passed away of pancreatic cancer on April 26, 1984, at Doctors' Hospital in Hollywood, Florida, at 79. More than two thousand mourners filled the Abyssinian Baptist Church in Harlem for his funeral, where Joe Williams sang Ellington's "Come Sunday," and he was buried beside his wife at Pinelawn Memorial Park in Farmingdale, New York. His autobiography, Good Morning Blues, written with Albert Murray, appeared in 1985. The orchestra carried on under a succession of directors beginning with Thad Jones, and the honors continued after his death: the Kennedy Center Honors (1981), the NEA Jazz Masters award (1983), the Presidential Medal of Freedom (presented posthumously on May 23, 1985), a Grammy Lifetime Achievement Award (2002), the New Jersey Hall of Fame (2009) and the Blues Hall of Fame (2019). His 1937 "One O'Clock Jump" entered the Library of Congress National Recording Registry in 2005, and his hometown named the Count Basie Center for the Arts in his honor.

Basie began as a stride pianist, shaped by James P. Johnson and Fats Waller, but the style tied to his name is the opposite of display. Britannica describes it as spare and economical, built on silence and on cutting a solo to the fewest notes that carry the rhythm and the feeling, where most of his peers were known for technical dash; a single comment from a bandsman in that account sums it up as doing very little and sounding wonderful. His comping, a few chords placed in the spaces behind the soloists, set the tone of an ensemble that AllMusic's William Ruhlmann calls a light, swinging rhythm section led from the piano, and Ruhlmann's judgment is that Basie's instrument was his band rather than any composition or solo of his own. The organ, taught to him by Waller, gave him a second voice that he used on sextet dates in the 1950s, on the Impulse! Kansas City 7 session, and on the Pablo duets with Oscar Peterson, where his brevity set off Peterson's speed. He came out of Kansas City's riff-and-blues tradition and, with Walter Page, Jo Jones and Freddie Green, helped fix the lighter four-beat pulse that later jazz rhythm sections inherited; he also admitted touches of bebop into the 1950s band as long as they made musical sense. The small-group sets of the Pablo years, with Zoot Sims, Roy Eldridge, Joe Pass, Milt Jackson and others, show the same lean touch applied to jam-session and trio settings. Nat Hentoff, writing about Loose Walk, noted that Basie was moved to play some robust stride piano that had not been heard from him in years.