Leo I

Leo I may refer to:

People

 * Pope Leo I (400–461), also known as Pope Saint Leo the Great
 * Leo I (emperor), Roman emperor from 457 to 474
 * Leo I, Prince of Armenia (d. 1140)
 * Leo I, King of Armenia (1150–1219), sometimes also referred to as Leo II, or Levon I the Magnificent, first king of Cilician Armenia

Other

 * LEO (computer), first computer used for commercial business applications
 * Leo I (dwarf galaxy), a dwarf galaxy that orbits the Milky Way Galaxy, and can be seen in the constellation of Leo
 * The Leo I Group, a group of galaxies also known as the M96 Group