For Whom the Bell Tolls is a novel by Ernest Hemingway published in 1940. It tells the story of Robert Jordan, a young American in the International Brigades attached to a republican guerrilla unit during the Spanish Civil War. As a dynamiter, he is assigned to blow up a bridge during an attack on the city of Segovia. Hemingway biographer Jeffrey Meyers writes that the novel is regarded as one of Hemingway's best works, along with The Sun Also Rises, The Old Man and the Sea, and A Farewell to Arms.

Hemingway wrote For Whom the Bell Tolls in Cuba, Key West, and Sun Valley, Idaho in 1939.[2] In Cuba, he lived in the Hotel Ambos-Mundos where he worked on the manuscript.[3][4] The novel was finished in July 1940, and published in October.[5][6] The novel is based on his experiences during the Spanish Civil War, with an American protagonist named Robert Jordan who fights with Spanish soldiers for the Republicans.[7] The novel has three types of characters: those who are purely fictional; those based on real people but fictionalized; and those who were actual figures in the war. Set in the Sierra de Guadarrama mountain range between Madrid and Segovia, the action takes place during four days and three nights. For Whom the Bell Tolls became a Book-of-the-month choice, sold half a million copies within months, was nominated for a Pulitzer Prize, and became a literary triumph for Hemingway.[7] Published on 21 October 1940, the first edition print run was 75,000 copies priced at $2.75.

A film adaptation of Hemingway's novel, directed by Sam Wood, was released in 1943 starring Gary Cooper and Ingrid Bergman. It was nominated for nine Academy Awards, including Best Picture, Best Actor and Best Actress; however, only the Greek actress Katina Paxinou won an Oscar for her portrayal of Pilar.

A television adaptation, directed by John Frankenheimer, was broadcast in two parts on CBS's Playhouse 90 in 1956, starring Jason Robards and Maria Schell as Robert Jordan and Maria, with Nehemiah Persoff as Pablo, Maureen Stapleton as Pilar, and Eli Wallach as the gypsy Rafael.