USNS John McDonnell (T-AGS-51) is an oceanographic survey ship that was operated by the United States Navy's Military Sealift Command.
The John McDonnell has been used by the military as primary a scientific ship. Its role has varied but is mostly dominated with the task of surveying the worlds underwater geological features using side scan radar. This information provides valuable navigation information and charts for both military and civilian ships to navigate unfamiliar territory. These ships were built to fill in the holes in the navigation charts. The John McDonnell has even aided in the location of two downed F-16s in the Northern Persian Gulf in 1993 and the wreckage of a Navy helicopter in the Strait of Hormuz in 1994. Two years later, it located a crashed F-14 in the Central Persian Gulf. In 2008, it helped locate a crashed Philippine C-130 Hercules in the Davao Gulf.
The Navy deactivated the ship on 25 August 2010 and as of August 2013, the General Services Administration was offering the ship at auction.