Zephaniah Platt (May 27, 1735 – September 12, 1807) was an American politician and lawyer, and founder of the U.S. town of Plattsburgh, New York.
Platt was born in Huntington (Long Island), New York, and received an English education. He was a direct descendant of Richard Platt [1] (1603–1684), who was born in Ware, Hertfordshire, England, and settled in the Connecticut Colony. Zephaniah Platt practiced law in Poughkeepsie, New York, and was a member of the New York Provincial Congress (1775–1777), Committee of Safety (1777), State Senate (1777–1783), Congress of the Confederation (1785 and 1786), Council of Appointment (1778 and 1781). He was a Dutchess County judge from 1781 to 1795 and delegate to the New York Constitutional Convention in 1788. He founded the town of Plattsburgh, New York, in 1788 and moved there in 1798 to continue practicing law. He was an originator of the Erie Canal, and was a regent of the State University of New York from 1791 until his death, in Plattsburgh, in 1807.
Of his sons, Jonas Platt, was a U.S. Representative; Charles Z. Platt was New York State Treasurer; and Zephaniah Platt was Michigan Attorney General.