The Lockheed Martin RQ-170 Sentinel is an American unmanned aerial vehicle (UAV) developed by Lockheed Martin and operated by the United States Air Force for the Central Intelligence Agency (CIA). While the USAF has released few details on the UAV's design or capabilities, defense analysts believe that it is a stealth aircraft fitted with aerial reconnaissanceequipment. Some images and details on the aircraft were released after Iran captured a RQ-170 in 2011.

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The RQ-170 Sentinel was developed by Lockheed Martin's Skunk Works as a stealth unmanned aerial vehicle (UAV). Journalists have noted design similarities between the RQ-170 and previous stealth and UAV programs such as the RQ-3 DarkStar and Polecat. It is a tailless flying wing aircraft, with pods, presumably for sensors or SATCOMs, built into the upper surface of each wing. Few details of the UAV's characteristics have been released, but estimates of its wingspan range from 38 feet (11.5m) to 90 feet (27 m). In a December 2012 report, journalist David Axe stated that "20 or so" RQ-170s had been built.

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The "RQ" designation indicates that the RQ-170 Sentinel does not carry weapons. Aviation Week's David A. Fulghum believes that the UAV is probably a "tactical, operations-oriented platform and not a strategic intelligence-gathering design".

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The USAF confirmed the "grainy photos of a gray, flying-wing-typed unmanned airplane near Kandahar Airfield."Since then, this aircraft has been known as "The Beast of Kandahar" in relation to the discussion of the RQ-170 Sentinel on 4 December 2009. A USAF colonel subsequently commented that RQ-170 is separate from the MQ-X program, which has yet to determine stealth or powerplant requirements, and thus the Sentinel will not replace the MQ-1 Predator and MQ-9 Reaper drones. As of May 2011, the U.S. military had not released any statements concerning the Sentinel since December 2009.

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The 30th Reconnaissance Squadron operates RQ-170 Sentinels. This squadron, which is based at Tonopah Test Range Airport in Nevada, was activated on 1 September 2005. RQ-170 Sentinels have been deployed to Afghanistan, where one was sighted at Kandahar International Airport in late 2007.This sighting, and the Sentinel's secret status at the time, led Bill Sweetman to dub it the "Beast of Kandahar".[16] The UAV being deployed to Afghanistan, despite the Taliban having no radar, led to speculation that the aircraft was used to spy on Pakistan or Iran: "Phil Finnegan, a UAV analyst at the Teal Group, an aerospace consulting firm, suggests the stealth capabilities are being used to fly in nearby countries. Neighboring Iran has an air force and air defense system that would require stealth technology to penetrate.