Klaatu may refer to:

  • Klaatu (The Day the Earth Stood Still), the humanoid alien protagonist in the 1951 science fiction film The Day the Earth Stood Still and its 2008 remake
    • Klaatu barada nikto, an iconic phrase from the film
  • Klaatu (Star Wars), a minor character from the original trilogy whose name was inspired by The Day the Earth Stood Still
  • Klaatu (band), a Canadian progressive rock group formed in 1973
  • Klaatu (comics), a Marvel Comics alien
  • Klaatu (podcaster), a technology journalist and educator