| Office: | Sheriff of Cook County |
| Term Start: | 1882 |
| Term End: | 1886 |
| Preceded: | Orrin L. Mann |
| Succeeded: | Canute R. Matson |
| Birth Date: | 30 March 1841 |
| Birth Place: | Chautauqua County, New York |
| Nationality: | American |
| Death Place: | Rockford, Iowa |
| Party: | Republican |
| Allegiance: | United States of America Union |
| Branch: | United States Army Union Army |
| Serviceyears: | 1861–1862, 1864–1865 |
| Rank: | Sergeant |
| Unit: | 9th Illinois Cavalry Regiment, 15th New York Volunteer Cavalry Regiment |
| Battles: | American Civil War |
Seth Hanchett (March 30, 1841 - January 6, 1905) was a Republican lawman and politician in Chicago who served as the Sheriff of Cook County from 1882 to 1886.
Born in Chautauqua County, New York in 1841, Hanchett settled in Chicago and entered the employ of the North Chicago City Railway Company in 1860. He enlisted in the 9th Illinois Cavalry Regiment of the Union Army at the outbreak of the American Civil War and was discharged due to illness within a year. Shortly afterward, Hanchett returned to New York and enlisted again. He saw service in the Valley campaigns of 1864 and was severely wounded by artillery fire at the Battle of Five Forks in 1865, resulting in the amputation of his entire left arm at the shoulder.[1]
Upon his return to Chicago after the war, Hanchett was superintendent of the city Soldier's Home and in 1867 was appointed bailiff of the County Court. He maintained his position as bailiff under four successive Cook County Sheriffs until the election of Charles Kern. Hanchett was elected Clerk of the Probate Court in 1877 and in 1882 was the Republican nominee for Sheriff, the office of which he won in a heated election. He served as Sheriff of Cook County until 1886.[1] Hanchett died in Rockford, Iowa in 1905.[2]