Séamus Turlough McElwaine (also spelt Seamus McElwain; 1 April 1960 – 26 April 1986) was a volunteer in the South Fermanagh Brigade of the Provisional Irish Republican Army (IRA) killed by the Special Air Service (SAS) while on active duty with Seán Lynch, who was seriously injured in the shooting.
McElwaine was the oldest of eight children and was born and grew up in Knockacullion, near Scotstown, County Monaghan, Republic of Ireland.
McElwaine took his first steps towards becoming involved in physical force republicanism when he joined Na Fianna Éireann aged 14. At the age of 16, McElwaine turned down an opportunity to study in the United States and joined the PIRA, stating "no one will ever be able to accuse me of running away".
McElwaine was an active member of the PIRA, who became Officer Commanding of the IRA in County Fermanagh by the age of 19. On 5 February 1980, McElwaine murdered off-duty Ulster Defence Regiment (UDR) corporal Aubrey Abercrombie as he drove a tractor in the townland of Drumacabranagher, near Florencecourt. Later that year, on 23 September, McElwaine murdered off-duty Royal Ulster Constabulary (RUC) Reserve Constable Ernest Johnston outside his home in Rosslea. He was suspected of involvement in at least 10 other murders.
On 14 March 1981, SAS soldiers surrounded a farmhouse near Rosslea, containing McElwaine and three other IRA members. Despite being armed with four rifles, including an Armalite, the IRA members surrendered and were arrested. While on remand in Crumlin Road Gaol McElwaine stood in the February 1982 Irish general election as an independent candidate for Cavan–Monaghan and received 3,974 votes (6.84% of the vote). In May 1982 McElwaine was convicted of murdering the RUC and UDR members, with the judge describing him as a "dangerous killer" and recommending he spend at least 30 years in prison.