John Sidney McCain, Jr. (January 17, 1911 - March 22, 1981) was an Admiral in the United States Navy. His father John S. McCain, Sr. was also an admiral in the Navy, and his son John S. McCain III is a US Senator representing Arizona.

Born in Council Bluffs, Iowa, he graduated from the United States Naval Academy in 1931.

During World War II, "Junior" – who preferred to be called "Jack" – commanded the submarines USS Gunnel and Dentuda. Subsequently he held a number of posts, rising to Commander-in-Chief of the United States Pacific Command before retiring in 1972.

He was involved in the investigations that followed the USS Liberty incident.

He is buried in Arlington National Cemetery.

USS John S. McCain (DDG-56) was named for him and his father.