Joel R. Poinsett, in full Joel Roberts Poinsett, (born March 2, 1779, Charleston, South Carolina, U.S.—died December 12, 1851, near Statesburg, South Carolina), American statesman noted primarily for his diplomacy in Latin America.
The son of a prominent South Carolina physician, Poinsett was educated in the United States and England and then traveled for seven years in Europe and western Asia. Returning home to serve in the approaching war with England, he was instead appointed the special agent for the United States in Buenos Aires and Chile in 1810.
After serving in the South Carolina legislature (1816–20), Poinsett was elected to the U.S. House of Representatives in 1820. He interrupted his legislative career to go on a special mission to Mexico in 1822 and 1823, publishing an account of his experiences in Notes on Mexico in 1824. In 1825 he became the first U.S. minister to Mexico, a post he held until 1829.
President Martin Van Buren appointed him secretary of war in 1837. Poinsett served until 1841 and then retired to his plantation in South Carolina, where he opposed the growing secessionist movement in his state.
An accomplished amateur botanist, Poinsett brought a flower from Mexico that was renamed the POINSETTIA in his honour. He was instrumental in founding the National Institute for the Promotion of Science and the Useful Arts, a precursor of the SMITHSONIAN INSTITUTION.