Jack Leon Ruby (born Jacob Leon Rubenstein; March 25, 1911 – January 3, 1967) was the Dallas, Texas nightclub owner who fatally shot Lee Harvey Oswald on November 24, 1963, while Oswald was in police custody after being charged with assassinating U.S. President John F. Kennedy and murder of Dallas policeman J. D. Tippit two days earlier. A Dallas jury found him guilty of murdering Oswald, and he was sentenced to death. Ruby's conviction was later appealed, and he was granted a new trial. However, on January 3, 1967, as the date for his new trial was being set, Ruby became ill in his prison cell and died of a pulmonary embolism from lung cancer.
In September 1964 the Warren Commission concluded that Ruby acted alone in killing Oswald. Various groups believed Ruby was involved with major figures in organized crime and that he killed Oswald as part of an overall plot surrounding the assassination of Kennedy.