Eugène Vieillard was a French physician and botanist.
Employed as a surgeon with the merchant navy, from 1855 to 1857 he collected plants in Tahiti with gardener-botanist Jean Armand Isidore Pancher. Afterwards, he spent a number of years conducting botanical investigations in New Caledonia, where he was a colleague to naturalist Émile Deplanche. Within this time period, he also collected ferns in New Zealand and visited the Cape of Good Hope and the island of Réunion. From 1871 to 1895, he was director of the botanical garden in Caen.
The plant genus Vieillardia was named in his honor by Jean Xavier Hyacinthe Montrouzier in 1860. More than 35 botanical species bear his name, a few examples being: Nepenthes vieillardii, Tristaniopsis vieillardii, Microsorum vieillardii and Dacrycarpus vieillardii. His name is also associated with a species of reptile found in New Caledonia, "Vieillard's chameleon gecko".