Harold C. Thomas, DE-21, was an Evarts-class destroyer escort. Mare Island Navy Yard launched her on 18 December 1942 as HMS Essington (BDE-21) for the Royal Navy. The United States took her over, and she was commissioned on 31 May 1943. She was named for Harold Chester Thomas, a Navy chief carpenter who was a lieutenant (junior grade) in the cruiser Boise. He was killed at the Battle of Cape Esperance on 11 and 12 October 1942, while working with damage control parties, and received the Navy Cross after his death.
She escorted merchant ships from San Francisco to Pearl Harbor three times and served with the submarine training command in November 1943. She reached Abemama in the Gilberts on 28 November with a convoy and spent the rest of the year on patrol and escort duty there. She sailed from Pearl Harbor on 29 February 1944 as flagship of Escort Division 10 and reached Eniwetok on 11 March. The Flintlock order of battle names her as an escort of the Northern Garrison Group, which reached Kwajalein on 5 February, but her own history places her at Pearl Harbor then. The two accounts do not agree. She sailed with the garrison convoys.
From 30 March 1944 she was part of a hunter-killer carrier group east of the Marshalls. For the rest of the year she shepherded merchant ships, cargo ships and transports through the rear areas to the assembly points of the invasion forces, from the Marshalls to the Admiralties, Palaus and Marianas. On 21 November she rescued seven men from a PBM flying boat that crashed off Majuro. After repairs on the west coast in January 1945 she returned to Pearl Harbor on 5 April and spent the rest of the war on submarine training and escort duty.
She reached San Pedro on 27 September 1945 and was decommissioned on 26 October. She was sold to the Pacific Bridge Company on 25 November 1946 and scrapped on 26 March 1947. She earned two battle stars.