John Allyne Gade (10 February 1875 – 16 August 1955) was an American architect, naval officer, diplomat, investment banker and author.
John Gade was born in Cambridge, Massachusetts as the son of Gerhard Gade (1834–1909) of Christiania (now Oslo), Norway, who was the American consul for Eastern Norway, and his American-born wife Helen Allyne. John Gade grew up at his father's estate Frogner Manor near Christiania. He was a brother of Fredrik Herman Gade, a nephew of Fredrik Georg Gade, Sr and a first cousin of Herman Gerhard Gade and Fredrik Georg Gade, Jr.
Gade had his early education in Norway. At the age of 13, he was sent to schools in Paris and later Braunschweig, Germany, where he became fluent in French and German in addition to his native English and Norwegian. Gade had wanted to enter West Point, but arrived too late to gain entry in 1892. He chose instead to study architecture at Harvard University.
After graduation Gade was offered a position with the architect firm of McKim, Mead and White in New York City. In 1907 he established his own office in New York City. In the fall of that year, he married Ruth Sibley of Rochester, New York.
Before the United States entered the World War I, Gade as a citizen of two neutral countries was able to join Herbert Hoover's U.S. Commission for Relief in Belgium, delivering food to the population under German occupation. Gade returned to the U.S. in April 1917. The subject was a friend of Franklin D. Roosevelt, the assistant secretary of the Navy and served in the Naval Reserve. The multi-lingual Gade was found useful by U.S. Naval Intelligence, and was commissioned as a Navy lieutenant and sent as Assistant Naval Attaché to Oslo and then in 1918 as Naval Attaché to Copenhagen and promoted to lieutenant commander.