Dr. John H. Watson is a fictional character in the Sherlock Holmes stories by Sir Arthur Conan Doyle. Along with Sherlock Holmes, Dr. Watson first appeared in the novel A Study in Scarlet (1887). "The Adventure of Shoscombe Old Place" (1927) is the last work of Doyle featuring Watson and Holmes, although their last appearance in the canonical timeline is in "His Last Bow." Throughout Doyle's novels, Watson is presented as Holmes's biographer. At the end of the first published Holmes story, A Study in Scarlet, Watson is so incensed by Scotland Yard claiming full credit for its solution that he exclaims: "Your merits should be publicly recognised. You should publish an account of the case. If you won't, I will for you". Holmes suavely responds: "You may do what you like, Doctor". Therefore, the story is presented as "a reprint from the reminiscences of John H. Watson", and most other stories of the series share this by implication.

Source: Wikipedia