English writer best known for the Swallows and Amazons series of children's novels (1930–47), which set the pattern for “holiday adventure” stories.

After studying science for only two terms at Yorkshire College, Leeds, Ransome pursued a literary career. His ambition was to be an essayist like William Hazlitt (Hazlitt, William) and to write books for children. In 1902 he moved to London, worked as an errand boy for publishers, and became a freelance writer of articles, stories, and reviews. His first book of significance, Bohemia in London (1907), is a partly autobiographical account of this period in his life. From 1908 to 1910 he edited a series of anthologies, The World's Story Tellers, and published a general History of Story-Telling (1909). He also wrote critical works on the writers Edgar Allan Poe (Poe, Edgar Allan) (1910) and Oscar Wilde (Wilde, Oscar) (1912); the latter led to an unsuccessful libel suit by Lord Alfred Douglas.

In 1913, largely to escape his unhappy first marriage (to Ivy Constance Walker, 1909; divorced 1924), Ransome went to Russia and studied native folktales, some of which he retold for English children in Old Peter's Russian Tales (1916). From 1915 to 1929 he was a newspaper correspondent based in Russia, Latvia, and Estonia. His articles and reports during World War I and from Russia after the Revolution of 1917 were vivid, insightful, and sometimes not welcomed by the British government. Although never himself a communist or socialist, he defended the Soviets in Six Weeks in Russia in 1919 (1919) and The Crisis in Russia (1921). In 1924 he married Evgenia Petrovna Shelepina, once a secretary to Leon Trotsky (Trotsky, Leon), and they settled in England.

Ransome traveled on assignment for the Manchester Guardian to Russia, Egypt, The Sudan, and China and sailed in the Baltic Sea. He described the latter experience in “Racundra's” First Cruise (1923), a small gem of sailing literature. He also wrote about another of his passions, angling, in a newspaper column and in books such as Rod and Line (1929) and Mainly About Fishing (1959). As an expert on Russia, he contributed relevant articles to the Encyclopædia Britannica in 1926. But he is most famous for 12 children's books, beginning with Swallows and Amazons (1930), which follow a number of resourceful boys and girls as they sail, camp, and have adventures, both real and imaginary. In these Ransome celebrated the outdoor activities he loved and the places in England, especially the Lake District, dearest to his heart. The sixth book in the series, Pigeon Post (1936), won the first Carnegie Medal for excellence in children's literature; however, its successor, We Didn't Mean to Go to Sea (1937), is widely considered Ransome's masterpiece.