John Knudsen Northrop (November 10, 1895 – February 18, 1981) was an American aircraft industrialist and designer who founded the Northrop Corporation in 1939.

His career began in 1916 as a draftsman for Loughead Aircraft Manufacturing Company (founded 1912). He joined the Douglas Aircraft Company in 1923, where in time he became a project engineer. In 1927 he joined the Lockheed Corporation, where he was a chief engineer on the Lockheed Vega transport. He left in 1929 to found Avion Corporation, which he sold in 1930. Two years later, he founded the Northrop Corporation. This firm became a subsidiary of Douglas Aircraft in 1939, so he co-founded a second company named Northrop.