USS Mero (SS-378), a Balao-class submarine, was a ship of the United States Navy named for the mero, any of several large groupers found in warm ocean waters.

Mero was laid down by Manitowoc Shipbuilding Co., Manitowoc, Wisc., 22 July 1944; launched 17 January 1945; sponsored by Mrs. Henry G. Taylor; and commissioned at Manitowoc 17 August 1945, Commander John H. Turner in command.

The last submarine built at Manitowoc, Mero got underway for shakedown in Lake Michigan 25 August; thence, between 6 September and 17 November she cruised the Great Lakes and visited several ports including Detroit, Cleveland, and Chicago. The Mero tied up at The Michigan Avenue bridge in Chicago and was open to visitors who were allowed aboard for a tour of the boat. Placed in floating drydock 9 November – 2 November, she reached New Orleans via the Mississippi River 29 November, on 6 December sailed for the Canal Zone, trained there a month, then sailed for Pearl Harbor 19 January 1946.

Mero reached Pearl 5 February and operated out of there until sailing for the west coast 22 February. Arriving San Francisco Bay 1 March, after preinactivation overhaul, she steamed to Mare Island 14 March to join the 19th Fleet, and decommissioned there 15 June 1946. Assigned to the Pacific Reserve Fleet, she remained berthed at Mare Island until loaned to Turkey 20 April 1960.

TCG Hızırreis (S 344)

For other ships with the same name, see TCG Hızırreis.

Mero was converted to a Fleet Snorkel submarine in 1960. On 20 April 1960 she was transferred, as a loan, to Turkey under the Military Assistance Program. The Turkish Navy renamed her TCG Hızırreis (S 344). After her voyage from San Francisco, Hızırreis was commissioned into Turkish Navy on 23 August 1960.

On 1 August 1973 ex-Mero was formally sold to Turkey and struck from the US Naval Vessel Register. She was discarded by the Turkish Navy in 1977 and used for spare parts.