Northern Spy also called 'Spy' and 'King', is a cultivar of domesticated apple that originated on the farm of Oliver Chapin in East Bloomfield, New York, in about 1840.

The Northern Spy was one of four apples honored by the United States Postal Service in a 2013 set of four 33¢ stamps commemorating historic strains, joined by Baldwin, Golden Delicious, and Granny Smith.

The white flesh is juicy, crisp and mildly sweet with a rich, aromatic subacid flavor, noted for high vitamin C content.

Its characteristic flavor is tarter than most popular varieties, and its flesh is harder or crunchier than most, with a thin skin.

A box of Northern Spies was sent to Senator Joseph McCarthy by the news staff of the Toronto Globe and Mail in 1953 as a joke.