French adventurer, trader, and publicist who was associated with the unsuccessful effort to establish French influence in northern Vietnam in 1873.

Dupuis began his commercial career in Egypt in 1858 but in 1860 moved to China, where he established himself first in Shanghai and, a year later, in Hankow. Dupuis learned Chinese and developed good relations with local officials while running a moderately successful business selling military equipment. He later claimed that as early as 1864 he had begun a search for a river route to the southwestern Chinese province of Yunnan and concluded that the route would be provided by the Red River. The best evidence, however, suggests that Dupuis did not think of exploiting the Red River for commerce until a French expedition led by Ernest Doudart de Lagrée and Francis Garnier (Garnier, Francis) passed through Hankow in 1868. The group was returning from an ascent of the Mekong River into Yunnan, and its members pointed out to Dupuis that the Red River might be used for trade with that province.

In 1871 Dupuis traveled down the Red River from Yunnan into Vietnam. He planned to use the river for a large shipment of arms to his Chinese customers, the army of Ma Ju-lung, in K'un-ming, the capital of Yunnan, and he went to Paris to seek official assistance. Although the French authorities would not provide overt backing, they did approve Dupuis's purchase of cannon in France and were ready to give some help with transport.

In November 1872 Dupuis sailed from Hong Kong with a well-equipped force, determined to carry his goods up the Red River, though he had no permission to do so from the Vietnamese government. By threats and bribery he overcame Vietnamese opposition to his plans and delivered his cargo in Yunnan. Returning to Hanoi, he found his Vietnamese associates imprisoned and his ships and men prevented from further commercial ventures on the Red River. He appealed to Admiral Marie-Jules Dupré (Dupré, Marie-Jules), the governor of French Cochinchina (southern Vietnam), for assistance.

Garnier, after serving in the Franco-German War, returned to the Far East; in November 1873 Dupré sent him with a small force of men to Hanoi. Garnier's official orders called on him to extricate Dupuis, but secret instructions given orally by Admiral Dupré apparently sanctioned aggressive action in northern Vietnam. With Dupuis's cooperation, Garnier attacked the Hanoi citadel and extended tenuous control over other parts of the Red River delta. When Garnier was killed on December 21, Dupré, having risked open conflict with French governmental policy, disavowed Garnier's actions and refused to heed Dupuis's plea that a French force be maintained in northern Vietnam.

Dupuis was financially ruined by these events. He returned to France, where he became a tireless advocate of a French advance into northern Vietnam and of himself as the discoverer of the commercial possibilities of the Red River. Among the best known of his numerous publications were Les Origines de la question du Tong-kin (1896; “The Origins of the Tonkin Issue”) and Le Tonkin de 1872 à 1886: histoire et politique (1910; “Tonkin from 1872 to 1886: History and Politics”). Despite his energy as an author and his earlier success in business, Dupuis faded into obscurity before his death in 1912.