Alexander De Witt (April 2, 1798 – January 13, 1879) was a 19th-century American politician from the state of Massachusetts.

[citation needed] An anti-slavery activist, De Witt later joined the Free Soil Party.

In January 1854, he was one of six signatories of the "Appeal of the Independent Democrats", drafted to oppose the Kansas-Nebraska Act.

[citation needed] He was defeated in his 1856 bid for reelection and returned to his previous work as a textile manufacturer.

De Witt later became a Republican, and supported the Union during the American Civil War by participating in efforts to recruit and equip soldiers for Massachusetts regiments.