Operation Barrel Roll was a covert U.S. Air Force 2nd Air Division and U.S. Navy Task Force 77, interdiction and close air support campaign conducted in the Kingdom of Laos between 14 December 1964 and 29 March 1973 concurrent with the Vietnam War.

The original purpose of the operation was to serve as a signal to the Democratic Republic of Vietnam (North Vietnam) to cease its support for the insurgency then taking place in the Republic of Vietnam (South Vietnam). This action was taken within Laos due to the location of North Vietnam's expanding logistical corridor known as the Ho Chi Minh Trail (the Truong Son Road to the North Vietnamese), which ran from southwestern North Vietnam, through southeastern Laos, and into South Vietnam. The campaign then centered on the interdiction of that logistical system. Beginning during the same time frame (and expanding throughout the conflict) the operation became increasingly involved in providing close air support missions for Royal Lao Armed Forces, CIA-backed tribal mercenaries, and Thai Volunteer Defense Corps in a covert ground war in northern and northeastern Laos. Barrel Roll and the "Secret Army" attempted to stem an increasing tide of People's Army of Vietnam (PAVN) and Pathet Lao offensives.

Barrel Roll was one of the most closely held secrets and one of the most unknown components of the American military commitment in Southeast Asia. Due to the ostensible neutrality of Laos, guaranteed by the Geneva Conference of 1954 and 1962, both the U.S. and North Vietnam strove to maintain the secrecy of their operations and only slowly escalated military actions there. As much as both parties would have liked to have publicized their enemy's own alleged violation of the accords, both had more to gain by keeping their own roles quiet. Regardless, by the end of the conflict in 1975, Laos emerged from nine years of war just as devastated as any of the other Asian participants in the Vietnam War.