Michael Rennie was a British film, television and stage actor, who had leading roles in a number of Hollywood films, including his portrayal of the space visitor Klaatu in the science fiction film The Day the Earth Stood Still (1951). In a career spanning more than 30 years, Rennie appeared in more than 50 films and in several American television series.

Klaatu is a fictional humanoid alien character best known from his appearances in the 1951 science fiction film The Day the Earth Stood Still and its 2008 remake. The character of Klaatu gained popularity partly due to the iconic phrase "Klaatu barada nikto!" associated with the character.