Uncle Oswald, or Oswald Hendryks Cornelius, is a fictional character created by Roald Dahl, who features in the short stories "The Visitor" and "Bitch", and the novel My Uncle Oswald.
Oswald Hendryks Cornelius, "the greatest fornicator of all time", is a womanizing gadabout, whose motto is never to sleep with one woman twice. He is an oenophile, scorpion and walking stick collector, opera lover, and an expert on Chinese porcelain. He is also wealthy, apparently as a result of morally dubious, maybe even illegal, schemes. In "The Visitor" Oswald stays with a wealthy Syrian and his beautiful wife and daughter; in "Bitch" he funds a scheme to create the perfect aphrodisiac; and in My Uncle Oswald he leads a scheme to sell famous men's sperm.
The stories and novel he appears in are introduced by an unnamed nephew (hence the prefix "Uncle") who, on Oswald's passing, inherits his life-spanning diaries, which contain the details of his many exploits.