Colonel Charles Paul Narcisse Moreau (14 September 1837, in Paris – 6 July 1916) was a French soldier and mathematician.
He introduced Moreau's necklace-counting function into mathematics, and achieved the worst result ever recorded in an international chess tournament.
He is sometimes said to have been a last-minute substitute for Mikhail Chigorin, who was apparently dropped after a dispute with the organizer Prince André Dadian, but Spinrad pointed out that this is unlikely because Moreau and Chigorin were both listed among the 14 competitors in a newspaper story in The New York Sun and Salt Lake Herald from 21 December 1902, several weeks before the tournament started on 10 February 1903.
Moreau (1873) pointed out a counterexample to a lemma used by Adrien-Marie Legendre in his attempt to prove Dirichlet's theorem on arithmetic progressions.
181–195) describes Moreau's analysis of the mathematical game "red and black" invented by Arnous de Rivière.