The Adventure of the Illustrious Client (1924) is one of the 56 Sherlock Holmes short stories written by British author Sir Arthur Conan Doyle, and one of the 12 stories collected as The Case-Book of Sherlock Holmes.

Sir James Damery comes to see Holmes and Watson about his illustrious client's problem (the client's identity is never revealed to the reader, although Watson finds out at the end of the story; it is heavily implied to be King Edward VII). General de Merville's young daughter Violet has fallen in love with the roguish and sadistic Austrian Baron Adelbert Gruner, who Damery and Holmes are convinced is a shameless philanderer and a murderer. The victim was his last wife, of whose murder he was acquitted owing to a legal technicality and a witness's untimely death. She met her end in the Splügen Pass. Holmes also finds out that the Baron has expensive tastes and is a collector and a recognised authority on Chinese pottery.Holmes's first step is to see Gruner, who is amused to see Holmes trying to "play a hand with no cards in it". The Baron will not be moved and claims that his charm is more potent than even a post-hypnotic suggestion in conditioning Violet's mind to reject anything bad that might be said about him. Gruner tells the story of Le Brun, a French agent who was crippled for life after being beaten by thugs after making similar inquiries into the Baron's personal business...

Famous works of the author Arthur Conan Doyle: A Study in Scarlet, The Sign of the Four, The Adventures of Sherlock Holmes, The Memoirs of Sherlock Holmes, The Hound of the Baskervilles, The Return of Sherlock Holmes, The Valley of Fear, His Last Bow, The Case-Book of Sherlock Holmes, Stories of Sherlock Holmes, The Lost World.