USS San Carlos (AVP-51) was a Barnegat-class seaplane tender built for the United States Navy during World War II.

After eleven years in reserve, San Carlos was converted to oceanographic research ship USNS Josiah Willard Gibbs (T-AGOR-1)—named after American scientist Josiah Willard Gibbs—and placed in service as a non-commissioned ship of the Military Sea Transportation Service from 1958 to 1971.

After overhaul there, she operated out of Coco Solo, Panama Canal Zone, from December 1945 through May 1946, and out of San Juan, Puerto Rico, from July 1946 to March 1947.

Alterations to her original design included the installation of six laboratories, a machine shop, a darkroom, a superstructure deck locker for experimental stowage or work, and a deep-sea winch capable of handling up to 40,000 feet (12,000 m) of wire rope and 20 long tons (20 t) of equipment.

For thirteen years she provided transportation, accommodations, and working spaces for American scientists and technicians investigating physical, chemical, and biological properties of the ocean.

Her large deep-sea winch and auxiliary propeller gave her the capability to investigate even the deep ocean trenches scattered throughout the world.

In July 1968, Josiah Willard Gibbs surveyed a large fracture zone crossing the Mid-Atlantic Ridge at 52°37′26″N 33°11′53″W / 52.624°N 33.198°W / 52.624; -33.198.