James W. Nesmith (July 23, 1820 - June 17, 1885) was a United States Senator and Representative from Oregon. Born in New Brunswick, Canada while his parents were on a visit from their home in Washington County, Maine, he moved with his father to Claremont, New Hampshire about 1828. He received a limited schooling, moved to Ohio in 1838 and Oregon in 1843, studied law, and was admitted to the bar but never practiced extensively. He engaged in agricultural pursuits and stock raising, and was elected judge of the provisional government of Oregon in 1845. He was captain in 1848 and 1853 of expeditions against hostile Indians, and was United States Marshal for Oregon from 1853 to 1855. He was superintendent of Indian affairs for Oregon and Washington Territories from 1857 to 1859.
Nesmith was elected as a Democrat to the U.S. Senate and served from March 4, 1861, to March 3, 1867; he was an unsuccessful candidate for reelection, and was appointed Minister to Austria, but his nomination was not confirmed. He served as road supervisor of Polk County in 1868, and was elected to the Forty-third Congress to fill the vacancy caused by the death of Joseph G. Wilson and served from December 1, 1873, to March 3, 1875; he did not seek renomination in 1874 to the Forty-fourth Congress. He died in Rickreall, Oregon in 1885; interment was in Polk County on the south bank of Rickreall Creek.
Joseph Gardner Wilson, Nesmith's cousin, and Clifton Nesmith McArthur, were both United States Representatives from Oregon.