Aerojet Rocketdyne is a subsidiary of American defense company L3Harris Technologies that manufactures rocket, hypersonic, and electric propulsive systems for space, defense, civil and commercial applications. Aerojet traces its origins to the General Tire and Rubber Company established in 1915, while Rocketdyne was created as a division of North American Aviation in 1955. Aerojet Rocketdyne was formed in 2013 when Aerojet and Pratt & Whitney Rocketdyne were merged, following the latter's acquisition by GenCorp from Pratt & Whitney. On April 27, 2015, the name of the holding company, GenCorp Inc., was changed to Aerojet Rocketdyne Holdings, Inc. Aerojet Rocketdyne Holdings was acquired by L3Harris in July 2023 for $4.7 billion.

Aerojet was an American rocket and missile propulsion manufacturer based primarily in Rancho Cordova, California, with divisions in Redmond, Washington, Orange and Gainesville in Virginia, and Camden, Arkansas. Aerojet was owned by GenCorp. In 2013, Aerojet was merged by GenCorp with the former Pratt & Whitney Rocketdyne to form Aerojet Rocketdyne.