USS Block Island (CVE-21/AVG-21/ACV-21) was a Bogue-class escort carrier for the United States Navy during World War II. She was the first of two escort carriers named after Block Island Sound off Rhode Island. Block Island was launched on 6 June 1942 by Seattle-Tacoma Shipbuilding Corporation of Seattle, Washington, under a Maritime Commission contract; sponsored by Mrs. H. B. Hutchinson, wife of Commander Hutchinson; transferred to the United States Navy on 1 May 1942; and commissioned on 8 March 1943, Captain Logan C. Ramsey in command. Originally classified AVG-21, she became ACV-21 on 20 August 1942, and CVE-21 on 15 July 1943.
Departing San Diego, California in May 1943, Block Island steamed to Norfolk, Virginia, to join the Atlantic Fleet. After two trips from New York City to Belfast, United Kingdom, during the summer of 1943 with cargoes of Army fighters.
She operated as part of a hunter-killer group. During her four anti-submarine cruises, Block Island′s planes sank two submarines: U-220 in 48°53′N 33°30′W on 28 October 1943 and U-1059 in 13°10′N 33°44′W on 19 March 1944. She shared credit with destroyer Corry and destroyer escort Bronstein for the sinking of U-801 in 16°42′N 30°20′W on 17 March 1944 and with Buckley for U-66 sunk on 6 May 1944 in 17°17′N 32°29′W. Thomas, Bostwick, Borie and Bronstein sank U-709 on 1 March 1943 and the same day Bronstein got U-603.
Block Island was torpedoed off the Canary Islands at 20:13 on 29 May 1944. U-549 had slipped undetected through her screen. The submarine put three torpedoes into the carrier before being sunk herself by Eugene E. Elmore and Ahrens of the screen in 31°13′N 23°03′W. The carrier lost 6 men in the attack; the remaining 951 were picked up by the escort screen.