John Peter Didier (1748–1823) was a U.S. politician and the first State Treasurer of Missouri.
John Peter Didier was reportedly a native of France. Prior to emigrated to the United States, he married Marie Elizabeth Mercier in Besançon, France on November 15, 1773. A prominent government official in the Missouri Territory, he served as Fire Captain in St. Louis, Missouri from 1811 to 1817. In 1817, he became Territorial Treasurer, serving in that post for a year. In 1820, he was appointed as the first State Treasurer following the signing of the state constitution, but before Missouri was officially admitted as a state. Along with the other provisional state officeholders, he resigned when Missouri officially became a state in August 1821. Public records indicate that he died two years later on August 25, 1823.