John Sidney “Slew” McCain Sr. was a U.S. Navy admiral. He held several command assignments during the Pacific campaign of World War II.

McCain was a pioneer of aircraft carrier operations who in 1942 commanded all land-based air operations in support of the Guadalcanal campaign, and who ultimately in 1944-1945 aggressively led the Fast Carrier Task Force, in the Pacific Ocean theater of World War II. His operations off the Philippines and Okinawa, and air strikes against Formosa and the Japanese home islands, caused tremendous destruction of Japanese naval and air forces in the closing period of the war. He died four days after the formal Japanese surrender ceremony.

He was the father of Admiral John S. McCain, Jr.; they became the first father-son pair ever to achieve four star admiral rank in the U.S. Navy. He was the grandfather of U.S. Senator from Arizona and 2008 Republican presidential nominee Navy Captain John S. McCain III and the great-grandfather of John S. McCain IV. All four generations graduated from the United States Naval Academy.