William Frederick McCoy QC (1886 – 4 December 1976) was an Ulster Unionist member of the Parliament of Northern Ireland for South Tyrone who went on to become an early supporter of Ulster nationalism. Born in Fivemiletown, County Tyrone, McCoy was educated at Clones High School and Trinity College Dublin, where he studied law. After serving in the British Army during World War I McCoy became a barrister in 1920 and held a number of leading legal positions in Northern Ireland including Crown Prosecutor for County Fermanagh (from 1926), Resident Magistrate for Belfast (1937–1943) and Senior Crown Prosecutor for Belfast (1949–1967).