John H. Watson, M.D. (born 7 July 1852, known as Dr. Watson, is a character in the Sherlock Holmes stories by Sir Arthur Conan Doyle. Watson is Sherlock Holmes's friend, assistant and sometime flatmate, and is the first person narrator of all but four stories in the Sherlock Holmes canon.

Watson is described as a crack shot and an excellent doctor and surgeon. Intelligent, if lacking in Holmes's insight, he serves as a perfect foil for Holmes: the ordinary man against the brilliant, emotionally-detached analytical machine. Conan Doyle paired two characters, different in their function and yet each useful for his purposes.

Watson is well aware of both the limits of his abilities and Holmes's reliance on him:

“Holmes was a man of habits... and I had become one of them... a comrade... upon whose nerve he could place some reliance... a whetstone for his mind. I stimulated him... If I irritated him by a certain methodical slowness in my mentality, that irritation served only to make his own flame-like intuitions and impressions flash up the more vividly and swiftly. Such was my humble role in our alliance. . The Adventure of the Creeping Man”.