Jakob Ignaz Hittorff (German: [ˈjaːkop ˈɪɡnaːts ˈhɪtɔʁf], French: [ʒak iɲas itɔʁf]) (Cologne, 20 August 1792 – 25 March 1867) was a German-born French architect who combined advanced structural use of new materials, notably cast iron, with conservative Beaux-Arts classicism in a career that spanned the decades from the Restoration to the Second Empire.

After serving an apprenticeship to a mason in his native city, he went in 1810 to Paris, and studied for some years at the Académie des beaux-arts working concurrently as a draughtsman for Charles Percier. At the Académie he was a favourite pupil of the government architect François-Joseph Bélanger, who employed him in the construction of one of the first cast-iron constructions in France, the cast-iron and glass dome of the grain market, Halle au Blé (1808–13); in 1814 Bélanger appointed him his principal inspector on construction sites. Succeeding Bélanger as government architect in 1818, he designed many important public and private buildings in Paris and also in the south of France. From 1819 to 1830 in collaboration with Jean-François-Joseph Lecointe he directed the royal fêtes and ceremonials, for which elaborate temporary structures were required, a post with a long history, which the two architects inherited from Bélanger. He also designed a new building for the Théâtre de l'Ambigu-Comique with Lecointe.