Flasher was a Gato-class submarine, SS-249, the first ship of the name. The name is a fish of the western Atlantic, also called the tripletail. Electric Boat at Groton laid her down on 30 September 1942 and launched her on 20 June 1943. The Dictionary of American Naval Fighting Ships commissions her on 26 September 1943. uboat.net and NavSource print 25 September. Reuben Thornton Whitaker was in command.
She reached Pearl Harbor from New London on 15 December 1943 and sailed on her first war patrol on 6 January 1944. Whitaker had her through four patrols and was relieved on 31 October 1944. George W. Grider had her for the fifth, which sailed in November for Cam Ranh Bay.
On the third patrol, in the South China Sea, she sighted the cruiser Oi with a destroyer. Two attacks sank the cruiser. That was 19 July 1944. The Dictionary credits the third, fourth, and fifth patrols with a Presidential Unit Citation, and all six of her war patrols with a battle star each.
She was still in service when the war ended. Bound for Guam on what would have been a seventh patrol, she was ordered back to New London. She was decommissioned and placed in reserve there on 16 March 1946. She was struck on 1 June 1959 and sold on 31 May 1963.