Théodore-Octave Girardet (22 September 1861, Versailles - 29 January 1935, Sainte-Maxime) was a French illustrator and wood-engraver.
His brothers, Jules, Eugène, Paul Armand and Léon, as well as his sister, Julia Antonine (1851-1921), also became painters or engravers.
He studied painting at the École Nationale Supérieure des Beaux-Arts in Paris with Alexandre Cabanel.
He eventually decided to specialize in wood-engraving and worked in the studios of Eugène Froment [fr].
He remained in Paris, where he specialized in wood-engravings which were used as illustrations for newspapers and magazines, such as Le Monde illustré, L'Illustration and Le Tour du Monde; often based on designs by his brother-in-law, Eugène Burnand, or other family members.