"The Adventure of the Blue Carbuncle" is a Sherlock Holmes short story by Sir Arthur Conan Doyle, first published in The Strand Magazine in January 1892 and later included in The Adventures of Sherlock Holmes. Set during the Christmas season, the story begins with Holmes investigating a curious incident involving a lost hat and a Christmas goose. As the case unfolds, it unexpectedly connects to the recent theft of a valuable gemstone from a London hotel, leading Holmes through a trail of clues that blend everyday mishaps with high-stakes crime.