The Cherry Valley massacre was an attack by British and Iroquois forces on a fort and the village of Cherry Valley in central New York on November 11, 1778, during the American Revolutionary War. It has been described as one of the most horrific frontier massacres of the war. A mixed force of Loyalists, British soldiers, Seneca and Mohawks descended on Cherry Valley, whose defenders, despite warnings, were unprepared for the attack. During the raid, the Seneca in particular targeted non-combatants, and reports state that 30 such individuals were slain, in addition to a number of armed defenders.

The raiders were under the overall command of Walter Butler, who exercised little authority over the Indian warriors on the expedition. Historian Barbara Graymont describes Butler's command of the expedition as "criminally incompetent". The Seneca were angered by accusations that they had committed atrocities at the Battle of Wyoming, and the colonists' recent destruction of their forward bases of operation at Unadilla, Onaquaga, and Tioga. Butler's authority with the Indigenous People was undermined by his poor treatment of Joseph Brant, the leader of the Mohawks. Butler repeatedly maintained that he was powerless to restrain the Seneca, despite accusations that he permitted the atrocities to take place.

During the campaigns of 1778, Brant achieved an undeserved reputation for brutality. He was not present at Wyoming — although many thought he was — and he actively sought to minimize the atrocities that took place at Cherry Valley. Given that Butler was the overall commander of the expedition, there is controversy as to who actually ordered or failed to restrain the killings. The massacre contributed to calls for reprisals, leading to the 1779 Sullivan Expedition which saw the total military defeat of the Iroquois in Upstate New York who allied with the British.