USS Aegir (AS-23) was the lead ship of the Aegir-class submarine tender in the United States Navy during World War II.

Aegir was laid down on 31 March 1943 under a Maritime Commission contract, MC hull 856, by the Ingalls Shipbuilding Company in Pascagoula, Mississippi and launched on 15 September 1943, sponsored by Mrs. James A. Sweeney.

On 23 October, the tender got underway for Pearl Harbor via the Panama Canal and San Diego.

[1] Aegir returned to the west coast of the United States on 11 September and was moored at the Mare Island Naval Shipyard.

Then in 1960 used as a maintenance ship at San Diego PacResFlt and then returned to Mare Island Naval Shipyard and remained there until her name was struck from the Navy list on 1 June 1971.