Giacomo Torelli (1 September 1608 – 17 June 1678) was an Italian stage designer, engineer, and architect. His work in stage design, particularly his designs of machinery for creating spectacular scenery changes and other special effects, was extensively engraved and hence survives as the most complete record of mid-seventeenth-century set design.
Torelli was born in Fano, where he may have first worked on amateur theatre productions at the Palazzo della Ragione, and he may also have gained experience in theatre design in nearby Pesaro or Urbino. His first documented work was in January 1641 for the opening of the Teatro Novissimo in Venice, where he was involved in the design of scenery and stage machinery for Francesco Sacrati's opera La finta pazza. This was followed with designs for two other works by Sacrati at the same theatre, Bellerofonte in 1642 and Venere gelosa in January 1643. He may also have worked on Francesco Cavalli's Deidamia, staged in 1644, also at the Teatro Novissimo. Torelli's last work in Venice was for Sacrati's L'Ulisse errante, performed during the carnival season of 1644 at the Teatro Santi Giovanni e Paolo.
When the Italian-born Cardinal Mazarin succeeded Cardinal Richelieu as the chief minister of France in 1642, he decided to introduce Italian opera to Paris. In June 1645 at the request of the regent Anne of Austria, the Duke of Parma sent Torelli to France to work on a production of La finta pazza in which Torelli largely repeated his designs for Venice. Mazarin had recruited Italian singers from Florence, but catering to French taste, comic ballet interludes choreographed by Giambattista Balbi replaced the choruses at the ends of the acts, and some of the recitative was spoken rather than sung. Performed in the large hall of the Petit-Bourbon beginning on 14 December 1645, the production was a great success, and the spectacular scenic effects created by Torelli were received with enthusiasm.