Billy Eckstine (8 July 1914 – 8 March 1993), born in Pittsburgh, Pennsylvania, USA as William Clarence Eckstein. He changed the spelling to Eckstine after a club owner said the original spelling was "too Jewish".

Eckstine was an American jazz singer and bandleader who also played trumpet, valve trombone, and guitar. He also performed briefly as Billy X. Stine. His nickname was Mr. B. Although best known as a singer, his openness to new music made him a strong influence on modern jazz, particularly bebop, as he gave employment to many of the musicians who founded the style.

After singing with the Earl Hines band from 1939 to 1943 he led his own band from 1944 to 1947. The band featured at various times a large number of rising jazz stars, including:

Saxophones: Gene Ammons, Dexter Gordon, Sonny Stitt, Lucky Thompson, Charlie Parker, Wardell Gray, Budd Johnson, Leo Parker Trumpets: Dizzy Gillespie, Miles Davis, Kenny Dorham, Fats Navarro Drums: Art Blakey Singers: Lena Horne, Sarah Vaughan

Eckstine later formed an octet, then went solo, becoming a popular ballad singer while remaining an important figure in jazz. His huge, distinctive baritone made him one of the first African American singers to have mainstream success. He was the composer of the blues classic "Jelly, Jelly" and also recorded the R&B top hit "Stormy Monday Blues" in 1942 (not to be confused with T-Bone Walker's 1947 "Call It Stormy Monday (But Tuesday Is Just As Bad)"). Most of his success as a singer came with ballads, including "Everything I have is Yours", "Blue Moon", "Caravan," "Prisoner of Love," "You Go to My Head," and "That Old Black Magic". His last hit was "Passing Strangers", a duet with Sarah Vaughan released in 1957.

Eckstine was a style leader and noted sharp dresser. He designed and patented a high roll collar that formed a B over a Windsor-knotted tie, which became known as a Mr. B. Collar. In addition to looking cool, the collar expanded and contracted without popping open, which allowed his neck to swell while playing his horns. The collars were worn by many a hipster in the late 1940s and early 1950s.

In 1984, Eckstine recorded his final album, I Am A Singer, featuring beautiful ballads arranged and conducted by Angelo DiPippo.