Born in Chabanais, Charente, Dupont first saw active service during the French Revolutionary Wars as a member of the Légion de Maillebois [fr] in the Netherlands, and in 1791 was on the staff of the Army of the North under General Théobald Dillon.

In the campaign on the Danube in 1805, as the leader of one of Michel Ney's divisions, Dupont earned further distinction, especially in the Battle of Haslach-Jungingen (Albeck), in which he prevented the escape of the Austrians from Ulm, and so contributed most effectively to the isolation and subsequent capture of Karl Mack von Leiberich and his whole army.

With a record such as but few of Napoleon's divisional commanders possessed, he entered Spain in 1808 at the head of a motley corps made up of provisional battalions and Swiss troops impressed into French service from the Spanish Royal Army (see Peninsular War).

Pursued and cut off by a Spanish army under the Captain General Castaños, his corps was defeated in the Battle of Bailén after his Swiss troops deserted and returned to their former allegiance.

An episode in the life of Pierre Dupont de l'Étang inspired the novel The Duel by Joseph Conrad (1908), which was turned into the film The Duellists, by Ridley Scott.

Over a period of roughly 20 years, Dupont de l'Étang fought a series of more than 20 duels with his fellow officer, the particularly quarrelsome Fournier, nicknamed by the Spaniards el demonio (Gabriel Féraud, in the film, and played by Harvey Keitel).

[2] Pierre Dupont was married on 26 December 1804 to Jeanne Grâce Bergon, daughter of a state counsellor, who died in the château des Ternes (Paris) on 13 June 1858.