Flower Power is the title of a photograph taken by American photographer Bernie Boston for the now-defunct newspaper The Washington Evening Star. Taken on October 21, 1967, during the March on the Pentagon by the National Mobilization Committee to End the War in Vietnam, the photo shows protester George Harris placing a carnation into the barrel of an M14 rifle held by a soldier of the 503rd Military Police Battalion (Airborne).

The March on the Pentagon was a massive demonstration against the Vietnam War on October 21, 1967. The protest involved more than 100,000 attendees at a rally by the Lincoln Memorial. Later about 50,000 people marched across the Potomac River to The Pentagon and sparked a confrontation with paratroopers on guard. The demonstrations were highly polarizing, and also produced the famous photograph of a protester placing flowers in a paratroopers' rifle.