Reginald Leo McKern (March 16, 1920–July 23, 2002), better known simply as Leo McKern, was an Australian actor who appeared in numerous British television programmes, movies and in over 200 stage roles.

Some notable roles:

• Horace Rumpole in the TV series Rumpole of the Bailey
• Number Two in the TV series The Prisoner (there were several Number Twos; the one played by McKern appeared in three episodes including the final two)
• Ryan in the film Ryan's Daughter
• Thomas Cromwell in the film, A Man for All Seasons (1966)
• The murderous holy man in the Beatles' movie Help
• The Prime Minister in The Mouse that Roared
• Imperius, the reclusive priest in Ladyhawke
• Several roles in the late 1950s television version of The Adventures of Robin Hood (which starred Richard Greene as Robin)
• A scientist in the film X the Unknown
• Cardinal Leone in the 1968 film The Shoes of the Fisherman.