USS Grampus (SS-207) was the eighth Tambor-class submarine to be commissioned in the United States Navy in the years leading up to the country's December 1941 entry into World War II.

On her first war patrol from 8 February to 4 April 1942, Grampus sank an 8636-ton tanker Kaijo Maru No.2 4 March 1942, the only kill of her short career,[7] and reconnoitered Kwajalein and Wotje atolls, later the scene of bloody but successful landings.

Air and water patrol in this area was extremely heavy and although she conducted several daring attacks on the 41 contacts she sighted, Grampus again was denied a kill.

In company with Grayback, Grampus departed Brisbane on 11 February 1943 for her sixth war patrol, from which she failed to return; the manner of her loss still remains a mystery.

A heavy oil slick was sighted there the following day, indicating that Grampus may have been lost there in a night attack or gun battle against the destroyers.