The fictional character Sherlock Holmes can never really die, since he never truly lived. Nevertheless, this didn't stop the creator of Sherlock Holmes, medical doctor and writer Sir Arthur Conan Doyle, from attempting to kill off his creation in one of his short stories, to no avail.
Sherlock Holmes was "born" in print as a fully-formed adult when he first appeared in a Conan Doyle novella entitled "A Study in Scarlet," which was first published in Beeton's Christmas Annual in December, 1887, then in book form as A Study in Scarlet in July, 1888.
The only direct reference to Holmes's age is in "His Last Bow. The War Service of Sherlock Holmes," published in 1917, in which Holmes is described as "a tall, gaunt man of sixty" at the time the story is set, which is 1914. Since A Study in Scarlet is set around 1880-1881, Holmes would have been about 26 or 27 years old at the time he appeared in his first story.
By 1891, Conan Doyle had written two novellas and over twenty short stories about Sherlock Holmes, and he was apparently becoming somewhat antagonistic towards Holmes. According to John Dickson Carr in his biography of Conan Doyle, in November of 1891 Doyle wrote to his mother, "I think of slaying Holmes ... He takes my mind from better things."
In the short story, "The Adventure of the Final Problem," published in The Strand magazine in December 1893, Conan Doyle tried to do just that in "The Final Problem."
In the story, Holmes and his arch-enemy, Professor Moriarty, engage in a violent struggle at the top of Reichenbach Falls in Switzerland, and they fall, "locked in each other’s arms," over 350 feet to their deaths into the gorge of the falls, "deep down in that dreadful caldron of swirling water and seething foam."
The public outrage and outcry at the death of Sherlock Holmes was so great that Conan Doyle "resurrected" Holmes in 1894 in a new series of short stories published in The Strand and later published in book form.
The final Holmes story written by Conan Doyle, "Shoscombe Old Place," was published in Liberty Magazine in March 1927, about three years before Conan Doyle died in July, 1930.
Sherlock Holmes didn't die with Conan Doyle, of course, and Holmes—now about 166 years old in fictional time—lives on in all of the many short stories, books, plays, television programs, and films that have featured him in the ninety years since Conan Doyle's death.