Increase Sumner (November 27, 1746 – June 7, 1799) was an American politician from Massachusetts. He served as the fifth governor of Massachusetts, serving from 1797 to 1799. Trained as a lawyer, he served in the provisional government of Massachusetts during the American Revolutionary War, and was elected to the Confederation Congress in 1782. Appointed to the Massachusetts Supreme Judicial Court the same year, he served in that post until 1797.