Théodore Ballu (8 June 1817 - 22 May 1885) was a French architect who designed numerous public buildings in Paris . He is the father of the politician Roger Ballu and the grandfather of the industrialist and politician Guillaume Ballu.
In 1840, Théodore Ballu won the Prix de Rome. That year competition’s final challenge was to design a palace for the Chambre des Pairs. Ballu designed the Église de la Trinité and directed the reconstruction of the Hôtel de ville, the city hall building in Paris, after a fire destroyed much of the original building..
The young laureate then left Paris and boarded at the Académie de France à Rome. He lived in the Villa Médicis from January 1841 to December 1845. He visited the ruins of Ancient Greece and his third year there was dedicated to Pompeii. In 1844-1845, his projects focused on the Érechthéion de l’Acropole d’Athènes.
Back in France, Théodore Ballu became an assistant to architect Franz Christian Gau on the Basilique Sainte-Clotilde construction site, then took charge after Gau's death in 1853. From then on, his career was much focused on his preference for religious buildings.
In 1860, he was named chief architect of Parisian buildings related to the religion. He then designed the Église de la Trinité (1861-1867), the Saint-Esprit temple on Rue Roquépine, and the churches of Saint-Ambroise (1863-1869) and Saint-Joseph (1866-1875).
He also directed the Saint-Jacques Tower restoration (1854-1858) and the construction of the Saint-Denis church in Argenteuil (1866).