The Thirty-Nine Steps is an adventure novel by John Buchan that first appeared as a serial in Blackwood's Magazine in August and September 1915 before being published in book form in October that year by William Blackwood and Sons, Edinburgh. It is the first of five novels featuring Richard Hannay, an all-action hero with a stiff upper lip and a miraculous knack for getting himself out of sticky situations.

The novel formed the basis for a number of film adaptations, notably: Alfred Hitchcock's 1935 version; a 1959 colour remake; a 1978 version which is perhaps most faithful to the novel; and a 2008 version for British television.

The Thirty-Nine Steps is one of the earliest examples of the 'man-on-the-run' thriller archetype subsequently adopted by Hollywood as an often-used plot device. In The Thirty-Nine Steps, Buchan holds up Richard Hannay as an example to his readers of an ordinary man who puts his country’s interests before his own safety. The story was a great success with the men in the First World War trenches. One soldier wrote to Buchan, "The story is greatly appreciated in the midst of mud and rain and shells, and all that could make trench life depressing."

Richard Hannay continued his adventures in four subsequent books. Two were set during the war when Hannay continued his undercover work against the Germans and their allies the Turks in Greenmantle (1916) and Mr Standfast (1919). The other two stories, The Three Hostages (1924) and The Island of Sheep (1936) were set in the post war period when Hannay's opponents were criminal gangs.

Major-General Sir Richard Hannay, KCB, OBE, DSO, Legion of Honour, is a fictional secret agent and army officer created by Scottish novelist John Buchan. In his autobiography, Memory Hold-the-Door, Buchan suggests that the character is based, in part, on Edmund Ironside, from Edinburgh, a spy during the Second Boer War.

Richard Hannay was one of the first modern spy thriller heroes and as such has heavily influenced the genre. Today, considered in the light of mainstream espionage fiction, Hannay appears to be badly clichéd, although, as he was created well before his attributes became clichéd, Hannay could be more accurately described as a seminal character of the spy thriller genre.

John Buchan, 1st Baron Tweedsmuir PC GCMG GCVO CH (26 August 1875 – 11 February 1940) was a Scottish novelist, historian and Unionist politician who served as Governor General of Canada, the 15th since Canadian Confederation.

After a brief legal career Buchan simultaneously began both his writing career and his political and diplomatic career, serving as a private secretary to the colonial administrator of various colonies in Southern Africa. He eventually wrote propaganda for the British war effort in the First World War. Once he was back in civilian life Buchan was elected Member of Parliament for the Combined Scottish Universities, but he spent most of his time on his writing career, notably writing The Thirty-Nine Steps and other adventure fiction.