An Empire ship is a merchant ship that was given a name beginning with "Empire" in the service of the Government of the United Kingdom during and after World War II. Most were used by the Ministry of War Transport (MoWT), which owned them and contracted their operation to various shipping companies of the British Merchant Navy.
Empire ships came from two main sources: new construction, and capture and seizure. New Empire ships were built for the MoWT or obtained from the United States to increase Britain's shipping capacity and offset losses to German U-boats, commerce raiders, bombing and other enemy actions in the tonnage war Germany was waging against Britain's sea transport around the globe. Others were captured or seized from enemy powers and some were acquired by requisition or normal purchase or lease.
New Empire ship construction represented an enormous undertaking that included classes of freighters, tankers, aircraft carriers, fast cargo liners, tank landing ships, Deep Sea Salvage and Rescue Tugs and several other categories. Total production numbered in the hundreds.
Empire ships were supplements to Britain's normal peacetime merchant fleet, swelling its wartime numbers to 12,000, then the largest merchant ship fleet in the world. Approximately 4,000 ships on the British register were lost between 1939 and 1945, a considerable number being sunk during the Battle of the Atlantic.
Significantly before Britain entered the Second World War on 3 September 1939, preparations had been in hand to put the shipping industry of Britain on a war footing. All shipbuilders had specified the capability of their yards to produce cargo ships, cargo liners, tramps, tankers, colliers, coasters and naval ships.
The Ministry of Shipping, formed in October 1939 quickly adopted a standard naming system, applying the prefix "Empire" for all merchant ships built in Great Britain for the Government. With some exceptions, the prefix was also extended to purchased or requisitioned ships and to those acquired as prizes.