Klaatu is one of the principal characters in the classic science fiction movie The Day the Earth Stood Still. Klaatu is famous in part due to the phrase "Klaatu barada nikto!", a favorite quote of film buffs.

Klaatu (played by Michael Rennie) arrives in a flying saucer in Washington, DC, wearing a silver spacesuit and accompanied by a large human-like robot, Gort (played by Lock Martin). Klaatu arrives as a peaceful ambassador from an extraterrestrial confederation, but is shot by one of the soldiers that form his rather apprehensive welcoming committee. To protect Klaatu, Gort vapourises all of the surrounding weaponry.

Klaatu is taken to a hospital, where he quickly recovers, and on learning that the government doesn't expect other nations to be willing to come to meet him, wants to get out to meet the people. The government wants to keep him in the hospital, so Klaatu escapes with a disguise, using the surname Carpenter. He finds a boarding house to stay in, and comes to know the people who live there, reads the Sunday morning paper, is shown around town by a young boy named Bobby Benson who stays there with his mother Helen, and drops by the home of Professor Barnhardt (a brilliant scientist) (Sam Jaffe).

Klaatu/Carpenter leaves a "calling card" by marking Barnhardt's calculations as a teacher would mark a student's. When Klaatu/Carpenter is brought by later by an army driver, Barnhardt discusses the situation with Klaatu, agrees to summon scientists from all nations, and asks Klaatu for a show of power that won't harm anyone, thus exhibiting that the extraterrestrial alliance controls enormous power that would threaten Earth if Earth threatens the peace in space.

Klaatu neutralizes electric power all over the world (with some notable exceptions, such as hospitals and airplanes in flight) for 30 minutes. Unfortunately, as a result, Klaatu is taken to be a threat and shot again.

However, Gort is programmed to defend Klaatu and will wreak havoc if anything untoward happens to him. Nearing death, Klaatu sends his friend Helen Benson (played by Patricia Neal) to deliver to the famous phrase that will cancel the attack. Helen reaches the robot, uttering "Gort! Klaatu barada nikto!" barely in time, whereupon Gort aborts his attack, retrieves Klaatu's corpse, transports him to the saucer, and revives him from death.

After Klaatu is revived, he steps out of the saucer, telling the onlookers - the scientists - that Earth, he tells them, can either decide to abandon warfare and join other spacefaring nations – a peace ensured by a massive deterrent force, the robot race Gort belongs to – or else be destroyed as a threat.

Film characters