For Whom the Bell Tolls is a novel by Ernest Hemingway published in 1940. It tells the story of Robert Jordan, a young American volunteer 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.

It was published just after the end of the Spanish Civil War (1936-1939), whose general lines were well known at the time. It assumes the listener knows that the war was between the government of the Second Spanish Republic, which many foreigners went to Spain to help and which was supported by the Soviet Union, and the Nationalist faction, which was supported by Nazi Germany and Fascist Italy. It was commonly viewed as the dress rehearsal for the Second World War. In 1940, the year the book was published, the United States had not yet entered the war, which had begun on September 1, 1939, with Nazi Germany's invasion of Poland.

The novel is regarded as one of Hemingway's best works.