USS Mahnomen County (LST-912) was an LST-542-class tank landing ship built for the United States Navy during World War II.

LST-912 was laid down on 5 February 1944, at Hingham, Massachusetts, by the Bethlehem-Hingham Shipyard; launched on 22 April 1944; sponsored by Mrs. Hazel B. Leppe; and commissioned on 21 May 1944.

At 02:55 Japanese planes attacked the task group and three hours later a "Val" careened into the LST killing four men, the vessel's only wartime casualties.

The next two days were spent under constant enemy fire until she steamed back to Leyte Gulf, arriving 17 January, to repeat the cycle.

She continued transport trips between Mindoro and Palawan until 12 March, when she departed for Manila with the 866th Engineer Aviation Battalion on board, arriving the following day.

[3] Following her arrival at Biak Island on 7 May, units of an RAAF airfield construction squadron came on board for an assault at Brunei Bay, Borneo on 10 June.

On 30 October 1946, she was returned to active status and departed the Washington Navy Yard for two years of duty with the Amphibious Force at Little Creek, Virginia.

She cruised the Mediterranean into 1949, visiting Sicily; Tripoli, Libya; Bizerte, Tunisia; Malta; and Marseille, France, before returning to Morehead City on 6 February 1949.

Assigned to Reserve LST Squadron 2, she served for the next three years in the 5th Naval District, operating along the Atlantic coast from New York to the Bahamas.

Mahnomen County was struck from the Naval Vessel Register on 31 July 1967, and, stripped of any salvageable materials, her hull was demolished by the Navy Support Detachment at Chu Lai.