"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 (1927). It was first published in Collier's in the United States in November 1924, and in The Strand Magazine in the United Kingdom in two parts, in February and March 1925.

The Case-Book of Sherlock Holmes is the final set of twelve Sherlock Holmes short stories by British writer Arthur Conan Doyle first published in the Strand Magazine between October 1921 and April 1927.