Jack in the Box is an American fast-food restaurant chain founded in 1951, by Robert O. Peterson in San Diego, California, where it is headquartered. The chain has over 2,200 locations, primarily serving the West Coast of the United States. Restaurants are also found in large urban areas outside the West Coast, as well as two in Guam. The company also formerly operated the Qdoba Mexican Grill chain until Apollo Global Management bought the chain in December 2017.

A fast-food restaurant, also known as a quick-service restaurant (QSR) within the industry, is a specific type of restaurant that serves fast-food cuisine and has minimal table service. The food served in fast-food restaurants is typically part of a "meat-sweet diet", offered from a limited menu, cooked in bulk in advance and kept hot, finished and packaged to order, and usually available for take away, though seating may be provided. Fast-food restaurants are typically part of a restaurant chain or franchise operation that provides standardized ingredients and/or partially prepared foods and supplies to each restaurant through controlled supply channels. The term "fast food" was recognized in a dictionary by Merriam–Webster in 1951.