Conan Doyle, the second of Charles Altamont and Mary Foley Doyle's 10 children, began seven years of Jesuit education in Lancashire, England, in 1868. After an additional year of schooling in Feldkirch, Austria, Conan Doyle returned to Edinburgh. Through the influence of Dr. Bryan Charles Waller, his mother's lodger, he prepared for entry into the University of Edinburgh's Medical School. He received his Bachelor of Medicine and Master of Surgery qualifications from Edinburgh in 1881 and an M.D. in 1885, upon completing his thesis, “An Essay upon the Vasomotor Changes in Tabes Dorsalis.”

While a medical student, Conan Doyle was deeply impressed by the skill of his professor, Dr. Joseph Bell, in observing the most minute detail regarding a patient's condition. This master of diagnostic deduction became the model for Conan Doyle's literary creation, Sherlock Holmes, who first appeared in "A Study in Scarlet" in Beeton's Christmas Annual of 1887. Other aspects of Conan Doyle's medical education and experiences appear in his semiautobiographical novels, The Firm of Girdlestone (1890) and The Stark Munro Letters (1895), and in the collection of medical short stories Round the Red Lamp (1894). His creation of the logical, cold, calculating Holmes, the “world's first and only consulting detective,” sharply contrasted with the paranormal beliefs Conan Doyle addressed in a short novel of this period, The Mystery of Cloomber (1889). Conan Doyle's early interest in both scientifically supportable evidence and certain paranormal phenomena exemplified the complex diametrically opposing beliefs he struggled with throughout his life.

Although public clamour prompted him to continue writing Sherlock Holmes adventures through 1926, Conan Doyle claimed the success of Holmes overshadowed the merit he believed his other historical fiction deserved, most notably his tale of 14th-century chivalry, The White Company (1891), its companion piece, Sir Nigel (1906), and his adventures of the Napoleonic war hero Brigadier Gerard and the 19th-century skeptical scientist Professor George Edward Challenger.

When his passions ran high, Conan Doyle also turned to nonfiction. His subjects include military writings, The Great Boer War (1900) and The British Campaign in France and Flanders, 6 vol. (1916–20), the Belgian atrocities in the Congo in The Crime of the Congo (1909), as well as his involvement in the actual criminal cases of George Edalji and Oscar Slater.

Conan Doyle married Louisa Hawkins in 1885, and together they had two children, Mary and Kingsley. A year after Louisa's death in 1906, he married Jean Leckie and with her had three children, Denis, Adrian, and Jean. Conan Doyle was knighted in 1902 for his work with a field hospital in Bloemfontein, South Africa, and other services during the South African (Boer) War (South African War).

Conan Doyle himself viewed his most important efforts to be his campaign in support of spiritualism, the religion and psychic research subject based upon the belief that spirits of the departed continued to exist in the hereafter and can be contacted by those still living on earth. He donated the majority of his literary efforts and profits later in his life to this campaign, beginning with The New Revelation (1918) and The Vital Message (1919). He later chronicled his travels in supporting the spiritualist cause in The Wanderings of a Spiritualist (1921), Our American Adventure (1923), Our Second American Adventure (1924), and Our African Winter (1929). He discussed other spiritualist issues in his Case for Spirit Photography (1922), Pheneas Speaks (1927), and a two-volume The History of Spiritualism (1926). Conan Doyle became the world's most renowned proponent of spiritualism, but he faced considerable opposition for his conviction from the magician Harry Houdini (Houdini, Harry) and in a 1920 debate with the humanist Joseph McCabe. Even spiritualists joined in criticizing Conan Doyle's article “The Evidence for Fairies,” published in The Strand Magazine in 1921, and his subsequent book The Coming of the Fairies (1922), in which he voiced support for the claim that two young girls, Elsie Wright and Frances Griffiths, had photographed actual fairies that they had seen in the Yorkshire village of Cottingley.

Conan Doyle died in Windlesham, his home in Crowborough, Sussex, and at his funeral, his family and members of the spiritualist community celebrated rather than mourned the occasion of his passing beyond the veil. On July 13, 1930, thousands of people filled London's Royal Albert Hall for a séance during which Estelle Roberts, the spiritualist medium, claimed to have contacted Sir Arthur.

Conan Doyle detailed what he valued most in life in his autobiography, Memories and Adventures (1924), and the importance that books held for him in Through the Magic Door (1907).