"A Study in Emerald" is a short story written by British fantasy and graphic novel author Neil Gaiman. The story is a Sherlock Holmes pastiche transferred to the Cthulhu Mythos universe of horror writer H. P. Lovecraft. It won the 2004 Hugo Award for Best Short Story.
The title is a reference to the Sherlock Holmes story A Study in Scarlet. "A Study in Emerald" first appeared in the anthology Shadows Over Baker Street, a collection of stories combining the worlds of Arthur Conan Doyle and H. P. Lovecraft, it has subsequently been printed in the anthology of Neil Gaiman's work, Fragile Things.