Merlin O'Neill (30 October 1898 – 1 March 1981) served as the tenth Commandant of the United States Coast Guard from 1 January 1950 to 1 June 1954.

In 1927, he began a three-year period as an instructor at the United States Coast Guard Academy before returning to sea in command of the USCGC Monaghan, in 1930.

[2] Newly commissioned as an ensign, O'Neill reported aboard the USCGC Gresham, homeported at New York City for his first assignment in April 1921.

In April 1922 he transferred to Seattle, Washington, to serve aboard the USCGC Haida whose primary area of operation was in the Bering Sea.

O'Neill assumed command of Ericsson for a short time before he was assigned to the Coast Guard Academy staff as an instructor in September 1927.

As a part of his headquarters assignment in June 1937 he attended the International Whaling Conference in London, England, as a technical advisor to the United States delegation.

[2] In October 1942, O'Neill assumed command of the Coast Guard manned Harris-class attack transport USS Leonard Wood which was practicing landings at Hampton Roads, Virginia, for the invasion of North Africa.

[2][7] As skipper of Leonard Wood O'Neill also particated in the Allied invasion of Sicily in July 1943, where he was awarded the Legion of Merit for exceptionally meritorious conduct in the performance of outstanding services during the landings.

[2] With the outbreak of the Korean War in June 1950 and the passage of the Magnuson Act, the Coast Guard became responsible for the security of all of the nation's ports and harbors.

[2][8] Under O'Neill's stewardship, the reorganization of the Coast Guard started by Commandant Farley was completed; this put into effect a system of comptroller functions that oversaw the financial affairs, centralized record-keeping, and standardized reports and forms.

O’Neill, who was recognized for his interest in the development and recognition of junior officers, moved to southern Maryland after his retirement and lived in the area until his death in 1981.