Lester Raymond Brown was born on March 14, 1912, in Reinerton, Pennsylvania, into a baker's family. His father played trombone, and Brown took up the saxophone at seven. The family moved to nearby Lykens, where he left school after ninth grade to enroll in 1926 at the Conway Military Band School (later part of Ithaca College) under the bandleader Patrick Conway. A music scholarship then took him to the New York Military Academy, from which he graduated in 1932. At Duke University, from 1932 to 1936, he led a campus dance band, Les Brown and His Blue Devils, which played on campus and along the East Coast and made its first records for Decca in 1936. After a long summer tour that year, some members went back to school and others stayed on the road with him, and by 1938 the group was the Les Brown Orchestra.

Brown spent a year in New York arranging for Jimmy Dorsey, Isham Jones and Larry Clinton before an RCA executive arranged a booking at the Hotel Edison in Manhattan, provided he could assemble a band. With a loan from his father he put together a twelve-piece group, regular radio broadcasts spread its name, and RCA Victor signed it to its Bluebird label. The band became a fixture on the radio series Spotlight Band, which reached servicemen around the country, and an announcer's 1942 introduction of "Les Brown and His Band of Renown" stuck as its permanent name. A teenage Doris Day was his first big vocalist but left within a year to marry, and her successor Betty Bonney sang on "Joltin' Joe DiMaggio" (1941), the band's first chart hit, a novelty about the Yankee outfielder's hitting streak. Day returned in 1943.

The song that defined the band came next. Brown, Ben Homer and the lyricist Bud Green wrote "Sentimental Journey," and the band recorded it with Day for Columbia on November 20, 1944, after the musicians' recording strike of 1942 to 1944 ended. Issued as Columbia 36769 with "Twilight Time" on the other side, it reached number one on the Billboard chart in 1945 and, arriving as the war in Europe ended, became an unofficial homecoming theme for returning servicemen. In 1946 Brown recorded an instrumental of Irving Berlin's "I've Got My Love to Keep Me Warm," arranged by Skip Martin (Columbia 38324); it became a million-seller and a top-ten record in 1949. In the mid-1940s his soloists included Abe Most and Ted Nash, but they drifted off to other work once Brown stopped touring and settled in Los Angeles.

A Hollywood Bowl engagement in early 1947 led him to rebuild the band from Los Angeles freelancers, and the same engagement started his longest association, with Bob Hope. Brown's band worked with Hope on radio, stage and television for almost fifty years, including 18 USO tours that reached more than three million service members. He led the orchestra on Doris Day's CBS radio show in 1952 and 1953, and the band was the house band on The Steve Allen Show from 1959 to 1961 and The Dean Martin Show from 1965 to 1972. On records he moved from Columbia to Coral and then Capitol, and the Los Angeles jazz players he hired fed other groups: tenor saxophonist Dave Pell, a Brown sideman from 1947 to 1955, formed his well-known octet in 1953 from some of Brown's sidemen.

The late 1950s and early 1960s were his most jazz-facing period on record. Concert Modern and Composer's Holiday (both Capitol, 1958), Stereophonic Suite for Two Bands (Kapp, recorded February 23 and 24, 1959, with Vic Schoen's orchestra) and the Coral LP Jazz Song Book (1960), on which Zoot Sims, Buddy DeFranco, Frank Rosolino and Mel Lewis played, show a band that could handle swing-era standards at a high level. Columbia then issued a run of show-music albums, The Lerner and Loewe Bandbook (1961), Play the Gershwin Bandbook (1961), The Richard Rodgers Bandbook (1962) and The Explosive Sound of Les Brown (1963). AllMusic notes that he was one of the founding members of the Recording Academy in the late 1950s.

The band kept working into old age. Goes Direct to Disc (1977) was cut straight to the lacquer for the audiophile label The Great American Gramophone Company, a 1983 festival album was issued in Japan with Georgie Auld and Buddy DeFranco as guests, and Digital Swing (Fantasy, 1987), recorded on November 21 and December 8, 1986 to mark the band's 50th anniversary, had Mundell Lowe on guitar. Brown led the band until 2000 and passed away from lung cancer on January 4, 2001, at 88, in Pacific Palisades; he is buried at Westwood Village Memorial Park in Los Angeles. He was survived by his wife Evelyn, his son Les Brown Jr. (1940 to 2023), who took over the band, and his daughter Denise. His grandson Jeff "Swampy" Marsh co-created the animated series Phineas and Ferb. Brown was inducted into the North Carolina Music Hall of Fame in 2010, and his hometown renamed a street near his birthplace Les Brown Lane in 2012.

Brown's band is not simple to classify. English Wikipedia calls him an American jazz musician, and AllMusic lists his genres as jazz and vocal, with styles of big band, swing, sweet bands, band music and traditional pop. That last cluster is the honest summary: the Band of Renown was a polished dance band whose biggest sellers were vocal pop records with Doris Day, Betty Bonney and others, and whose steadiest work was on radio, television and USO stages for Bob Hope, Steve Allen and Dean Martin. AllMusic's Scott Yanow calls it a jazz-oriented dance band and also says it was not really a jazz band, but that it used enough jazz elements and enough strong soloists to be taken seriously by jazz players and by the jazz press of the 1940s.

The Blue Devils at Duke modeled their sound on the Casa Loma Orchestra, and from 1940 Brown made more room for his soloists. He seldom featured himself, though AllMusic calls him a good player. His arrangers, among them Skip Martin and Frank Comstock, favored crisp, precise ensemble writing, and several of the Los Angeles jazz players who passed through the band, such as Dave Pell, Ronnie Lang, Ray Sims and Don Fagerquist, went on to West Coast studios and small groups. Critically he is remembered as the leader of an unusually durable and respected swing band rather than as an innovator, which is how Yanow puts it too.