Telefon is a 1977 spy film directed by Don Siegel and starring Charles Bronson, Lee Remick and Donald Pleasence. The screenplay by Peter Hyams and Stirling Silliphant is based on the 1975 novel by Walter Wager.

After the Cuban Missile Crisis, the Soviet Union planted a number of long-term, deep-cover sleeper agents all over the United States, who were so thoroughly brainwashed that even they did not know they were agents. They can be activated only by a special code phrase, a line from the Robert Frost poem "Stopping by Woods on a Snowy Evening" – followed by the agent's real first name. Their mission was to sabotage crucial parts of the civil and military infrastructure in the event of war.

Years later, Nikolai Dalchimsky, a rogue KGB headquarters clerk, travels to America and takes with him the Telefon Book, which contains the names, addresses and telephone numbers of all the sleeper agents. He starts activating them, one by one. American counterintelligence is thrown into confusion when seemingly-ordinary citizens start blowing up facilities that were once important but now have little, if any, value. The agents either commit suicide or die in the act itself.

The KGB does not dare tell its political leaders, much less the Americans, about its negligence in not deactivating the spy network. KGB Major Grigori Borzov, who was selected in part for his photographic memory, memorizes the contents of the only other copy of the Telefon Book and is sent to find and stop Dalchimsky quietly, before either side learns what is happening and possibly starts a war. Borzov is given the assistance of only a single agent, Barbara, who had been planted in America years before.

Eventually, Borzov realizes the method behind Dalchimsky's pattern of attacks: he has chosen the agents by the first letters of their American hometowns by "writing" his own name in sabotage across America. Borzov thus anticipates Dalchimsky's next chosen agent and kills Dalchimsky.

However, there are a number of twists. Barbara has orders from the KGB to assassinate Borzov once he succeeds to get rid of a dangerous loose end. In addition, she is a double agent and actually works for America. When she informs her American superior, Sandburg, he also tells her to kill Borzov so that she will retain the confidence of the KGB. However, Barbara has fallen in love with her would-be target. She informs Borzov, and together, they blackmail both sides into leaving them alone by holding the threat of the remaining Telefon agents over their heads.

MGM bought the film rights to the novel in October 1974. The novel was published in April 1975. The New York Times called the novel "a doozie of a thriller".

Peter Bellwood was the first writer. Then Peter Hyams wrote a script. Hyams says Dan Melnick then head of MGM told him he wanted Hyams to write and direct, but his last film Peeper had flopped and Hyams said "he knew there was no way he was going to let me direct it." They did like the script but brought in Richard Lester to direct. Hyams rewrote the script for Lester, who then left the project and Don Siegel came on board. Hyams would leave to make Capricorn One and Stirling Silliphant rewrote the script.