Powhatan Ellis (January 17, 1790 - March 18, 1863) was a United States Senator from Mississippi. Born at "Red Hill" in Amherst County, Virginia, he graduated from Washington Academy (now Washington and Lee University) in 1809, attended Dickinson College Carlisle, Pennsylvania in 1809 and 1810, and studied law at William and Mary College in 1813 and 1814. He was admitted to the bar and commenced practice in Lynchburg, Virginia; he moved to Natchez, Mississippi in 1816 and continued the practice of law.
Ellis was a judge of the Mississippi Supreme Court from 1823 to 1825, and was appointed to the U.S. Senate to fill the vacancy caused by the resignation of David Holmes, and served from September 28, 1825, to January 28, 1826, when a successor was elected and qualified; he was an unsuccessful candidate for election to fill the vacancy. He was elected to the Senate and served from March 4, 1827, to July 16, 1832, when he resigned to accept a judicial position.
From 1832 to 1836, Ellis was judge of the United States District Court for the district of Mississippi, and was appointed by President Andrew Jackson as Charge d'Affaires of the United States to Mexico, serving from January to December 1836, when he closed the legation. He was appointed by President Martin Van Buren as United States Minister Plenipotentiary to Mexico, holding that office from 1839 to 1842. He moved to Richmond, Virginia, where he died in 1863; interment was in Shockoe Cemetery.