The Third Force was the name given to a number of attempts by Northern Irish politician Ian Paisley, then leader of the Democratic Unionist Party (DUP), to create an Ulster loyalist 'defensive militia'.
The best known example was the Third Force rallies on 1 April 1981. At a number of these rallies, large groups of men displayed what purported to be firearms certificates. Rallies were held on hillsides near Gortin, Newry, and Armagh. At Gortin the Royal Ulster Constabulary (RUC) were attacked and two vehicles overturned. On 3 December 1981, Paisley said that the Third Force had between 15,000 and 20,000 members.
The group was established by Paisley as a complement to the security forces (Paisley had previously been associated with the Ulster Protestant Volunteers loyalist paramilitary group). It grew from opposition to the increasing pace of co-operation between the governments of the United Kingdom and Republic of Ireland, as well as in response to the murder of Robert Bradford. The group largely disappeared with the emergence of Ulster Resistance.