John Anthony Walker Jr. (July 28, 1937 – August 28, 2014) was an American criminal and spy. He served as a United States Navy Chief Warrant Officer and communications specialist. He was convicted of spying on the United States working for the Soviet Union from 1968 to 1985.
After Walker's arrest, Caspar Weinberger, President Ronald Reagan's Secretary of Defense, concluded that the Soviet Union made significant gains in naval warfare attributable to Walker's spying.
Walker died August 28, 2014, while still in prison. He would have been eligible for parole in 2015.