John or Jack Leonard may refer to:John Leonard (songwriter), early 19th century radical poet and songwriter, probably born in Gateshead John Leonard (critic) (1939–2008), American literary, television, film, and cultural critic John Leonard (poet), Australian poet John Leonard, Gaelic footballer John Leonard (canoeist), New Zealand sprint canoeist John Leonard (judge) (1926–2002), British judge Johnny Leonard (1903–1995), Australian rules footballer John B. Leonard (1864–1945), American civil engineer John J. Leonard, American roboticist and professor at MIT Jack Leonard (footballer) (1876–?), English footballer Jack Leonard (hurler) (1873–1938), Irish hurler Jack E. Leonard (1910–1973), American comedian and actor John E. Leonard (1845–1878), United States Representative from Louisiana J. William Leonard, director of the Information Security Oversight Office John Leonardi (1541–1609), Catholic saint whose feast day is on 9 October John Leonard (bishop) (1829–1908), Irish bishop John W. Leonard (1890–1974), US Army general John Leonard, Baron Leonard (1909–1983), British Labour Party politician John Leonard, , American ice hockey player John Leonard (architect), English architect