Seven ships of the United States Navy have borne the name USS Grampus, for two members of the dolphin family (Delphinidae): Grampus griseus, also known as Risso's Dolphin, and Orcinus orca, also known as the orca.

• The first Grampus, 12, a schooner built to suppress piracy and catch slavers, had a small part in the Amistad trials.

• The second Grampus was a side-wheel steamer, originally Ion, used as a receiving ship for the Mississippi Squadron during the American Civil War.

• The third USS Grampus, a 352-ton stern-wheel gunboat armed with two brass 12 pounders (5 kg), was originally CSS Grampus, scuttled by the Confederates on 7 April 1862 to prevent her capture. However, the Union Gunboat Flotilla raised her during May 1862, and she is believed to be the Grampus No. 2 that burned the following 11 January.

• The fourth Grampus (SS-4) was Submarine Torpedo Boat No. 4, which was renamed A-3 and patrolled Manila Bay during World War I.

• The fifth USS Grampus, originally Boothbay, was 1708 tons and 126 feet long, built by Neafie and Levy , of Philadelphia, Pennsylvania. She was purchased from the Eastern Steamship Line of Boston, Massachusetts and commissioned 14 December 1917, at the Boston Navy Yard. Her name was changed to Grampus in November 1920. She was assigned to ferry service between the Washington Navy Yard, Indian Head, Maryland, and Dahlgren, Virginia. Grampus decommissioned 11 December 1930. Her name was struck from the Naval Vessel Register on 30 December 1930, and she was later sold to the Buxton Line of Norfolk, Virginia.

• The sixth Grampus (SS-207), a Tambor-class submarine, was lost during World War II. See also List of U.S. Navy losses in World War II

• The seventh Grampus (SS-523) a Tench-class submarine, served through most of the Cold War, then was sold to Brazil.

See also HMS Grampus and CSS Grampus.