Peter Joseph Cleary was an Irish republican and a leading member of the 1st Battalion of the Provisional Irish Republican Army's South Armagh Brigade. He held the rank of Staff Officer and served as the unit's treasurer. He was implicated by journalist and author Joe Tiernan in the killing of Ulster Defence Regiment corporal and alleged Ulster Volunteer Force member Robert McConnell. Ten days after McConnell's killing, Cleary was shot dead by the Special Air Service after being arrested at the home of his girlfriend outside Forkhill. He was widely believed to have been the mastermind behind the Kingsmill massacre, when ten Ulster Protestant workers were taken from their work van and shot dead by the roadside. He was the first person in Northern Ireland to be killed by the SAS, following the admission of their deployment there in January 1976. According to the SAS, he was shot after attempting to take the rifle from the officer who was guarding him in a bid to escape.