Jack Ruby, American businessman and murderer (b. 1911)
Jack Leon Ruby (born Jacob Leon Rubenstein; April 25, 1911 – January 3, 1967) was an American nightclub owner who murdered Lee Harvey Oswald when he fatally shot him on November 24, 1963, while Oswald was in police custody after being charged with both the murder of John F. Kennedy, the incumbent United States president, and the murder of Dallas policeman J. D. Tippit. A Dallas jury found Ruby guilty of murdering Oswald and sentenced him to death.

Ruby's conviction was later appealed, and he was granted a new trial. However, as the date for his new trial was being set, Ruby became ill in prison and died of a pulmonary embolism from lung cancer on January 3, 1967.

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.