This is a detective mystery novel written by Sir Arthur Conan Doyle, introducing his new character of Sherlock Holmes, who later became one of the most famous literary detective characters. He wrote the story in 1886, and it was published the next year. The book's title derives from a speech given by Holmes to his sidekick Doctor Watson on the nature of his work, in which he describes the story's murder investigation as his "study in scarlet": "There’s the scarlet thread of murder running through the colourless skein of life, and our duty is to unravel it, and isolate it, and expose every inch of it."

The story, and its main character, attracted little public interest when it first appeared. Only 11 complete copies of Beeton's Christmas Annual 1887 are known to exist now and they have considerable value. Although Conan Doyle wrote 56 short stories featuring Holmes, A Study in Scarlet is one of only four full-length novels in the original canon. The novel was followed by The Sign of Four, published in 1890. A Study in Scarlet was the first work of fiction to incorporate the magnifying glass as an investigative tool.