Port admiral is an honorary rank in the United States Navy, and a former appointment in the British Royal Navy.
In British naval usage, the term 'port admiral' had two distinct (and somewhat contradictory) meanings, one generic, one specific.
Historically, 'port admiral' was used as a generic term for the senior naval officer having authority over all commissioned ships and naval personnel stationed at a particular home base or anchorage. (Those appointed as Flag Officers Commanding or Commanding-in-Chief of a particular area or Fleet often functioned as the local port admiral in this sense.)
By this definition, the port admiral did not have oversight of the local Royal Navy Dockyard (if any); Dockyards (including ships laid up 'in ordinary') were overseen by an independent official: usually a resident Commissioner appointed by the Navy Board (prior to 1832) or an Admiral-superintendent appointed by the Admiralty (1832-1971). The distinction is seen in informal correspondence such as the following, dated 1837: "The Devonport regatta ... was attended by the Port-Admiral, the Admiral-Superintendent of the Dockyard ... and other persons of consideration."
In practice the offices of port admiral and admiral-superintendent were sometimes combined.
In 1971 the remaining Admirals-Superintendent of HM Dockyards were redesignated as Port Admirals; unlike the above use of the term, this was an official designation. This reflected a consolidation of previously distinct command roles, and coincided with the appointment of civilian Dockyard General Managers to oversee work within the Dockyards across all departments.
Today, both uses of the term are obsolete (as far as current naval practice is concerned) as the equivalent appointments are not of flag-officer rank.
Port admiral is an honorary rank in the United States Navy for the senior officer of the ships in a naval dockyard. Examples include Samuel Livingston Breese from 1869 to 1870 in Philadelphia. The port admiral usually has a flagship, examples of which include USS Roanoke for the New York City port admiral from 1865 to 1874.