The Marias Massacre (also known as the Baker Massacre or the Piegan Massacre) was a massacre of Piegan Blackfeet Native peoples committed by United States Army forces under Major Eugene Mortimer Baker as part of the Indian Wars. The massacre occurred on January 23, 1870, in Montana Territory. Approximately 200 Native people were killed, most of whom were women, children, and older men.
As part of a campaign to suppress Mountain Chief's band of Piegan Blackfeet, the U.S. Army attacked a different band led by Chief Heavy Runner, to whom the United States government had previously promised their protection. This resulted in public outrage and a long-term shift towards a "Peace Policy" by the Federal Government, as advocated by President Ulysses S. Grant.