Charles Armand Auguste Ferdinand Mercier du Paty de Clam (21 February 1853 – 3 September 1916) was a French army officer, an amateur graphologist, and a key figure in the Dreyfus affair.

In late September 1894, French military intelligence became aware of a spy within the army through a handwritten note (the bordereau) obtained by their agent within the German embassy in Paris.

Du Paty de Clam, then a major attached to the General Staff, was heavily involved in the investigation to find the spy, due principally to his expertise in graphology (handwriting analysis).

In mid-October 1894 an unsuspecting Dreyfus was summoned to a meeting with Major du Paty de Clam, two (civilian) police detectives and a man from French military intelligence.

In November 1897 du Paty de Clam was also involved in further threatening letters sent by Esterhazy to Picquart and the Dreyfusards' chief ally within the government, Senator Auguste Scheurer-Kestner.

[3] Following the arrest and suicide of his co-conspirator Major Henry and Esterhazy fleeing to England (both in August, 1898),[1] the army made du Paty de Clam 'inactive' in September 1898.

His son, Charles du Paty de Clam, was appointed Commissioner-General for Jewish Affairs under the Vichy government between February and May 1944, mainly because his father had been Alfred Dreyfus's accuser.

He was a social acquaintance of the German military attaché Maximilian von Schwartzkoppen who referred to him as "having a touch of the blundering and erratic" which made him unsuited to the role required of him as a senior officer of the General Staff.