Theodore Sedgwick III (January 27, 1811 – December 9, 1859) was an American attorney and author on legal topics. He was born in Albany, New York, the son of Theodore Sedgwick II (1780–1839) and Susan Anne Ridley Sedgwick (1788–1867). He was a grandson of Theodore Sedgwick (1746–1813). He graduated from Columbia College in 1829. He then studied law and was admitted to the bar in May, 1833. Sedgwick died in Stockbridge on December 9, 1859. He was buried at Stockbridge Cemetery.