Duke of Greystoke is a title in the Peerage of Great Britain held by members of the Clayton family. Edgar Rice Burroughs simply refers to members of the family in his Tarzan novels as "Lord Greystoke"; in Tarzan Alive, Philip José Farmer refers to the family's senior title as that of Duke.

John Cecil Clayton, 1st Duke of Greystoke

John Cecil Clayton, fifth Earl Staveley and 14th Baron Grebson, was a child prodigy who on reaching his majority worked to derive great wealth from slavery, and great influence through lending the profits to King George II. He was created first Duke and Viscount Greystoke for thwarting a Jacobite assassin with designs upon the life of the king. He was the father of both the 2nd and 3rd Dukes.

‎Sir Jesse Clayton, 4th Duke of Greystoke

An energetic businessman and miser who rebuilt the family fortunes.

Philip José Farmer has identified the 4th Duke as, somewhat loosely, the basis for the character of Manchester bagman-turned-baronet Sir Jesse Trefusis in George Bernard Shaw's novel An Unsocial Socialist (Sir Jesse's son Sidney is the protagonist).

John Clayton, 5th Duke of Greystoke

The fifth Duke of Greystoke was identified as John Clayton, a London cabdriver who briefly appears in the Sherlock Holmes story The Hound of the Baskervilles, by Professor H.W. Starr in his article "A Case of Identity, or The Adventure of the Seven Claytons" (reprinted in Tarzan Alive). Following Professor Starr's speculation that the only thing likely to have driven the Duke to the life of a working man was an enthusiasim for Socialism, Philip José Farmer was able to identify the Duke as the basis for Sidney Trefusis, son of Sir Jesse. The Duke was murdered by Peter Michael Carey following an unsuccessful attempt by the latter to blackmail him.

William Cecil Clayton, 6th Duke of Greystoke

In a modification of Professor Starr's theories, Tarzan Alive states that William Cecil Clayton succeeded his elder brother in the title. The 6th Duke, who had been a peer in his own right during his brother's lifetime, has been identified with the Duke of Holdernesse or Greyminister mentioned in the Sherlock Holmes stories "The Adventure of the Priory School" and "The Blanched Soldier", and was the father (through an affair with Patricia Clarke Wildman) of Clark Savage, Sr.

John Clayton, 8th Duke of Greystoke

Better known simply as Tarzan of the Apes.

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