Operation Ranch Hand was a U.S. military operation during the Vietnam War, lasting from 1962 until 1971. Largely inspired by the British use of chemicals 2,4,5-T and 2,4-D during the Malayan Emergency in the 1950s, it was part of the overall herbicidal warfare program during the war called "Operation Trail Dust". Ranch Hand involved spraying an estimated 19 million U.S. gallons (72,000 m3) of defoliants and herbicides over rural areas of South Vietnam in an attempt to deprive the Viet Cong of food and vegetation cover. Areas of Laos and Cambodia were also sprayed to a lesser extent. According to the Vietnamese government, the chemicals caused 400,000 deaths. The United States government has described these figures as unreliable.

Agent Purple is the code name for a powerful herbicide and defoliant used by the U.S. military in their herbicidal warfare program during the Vietnam War. The name comes from the purple stripe painted on the barrels to identify the contents. Largely inspired by the British use of herbicides and defoliants during the Malayan Emergency, it was one of the so-called "Rainbow Herbicides" that included the more infamous Agent Orange. Agent Purple and Orange were also used to clear brush in Canada.