James Martin Pacelli McGuinness (Irish: Máirtín Mag Aonghusa; born in Derry on 23 May 1950) is an Irish politician and the current Deputy First Minister of Northern Ireland.

A Sinn Féin politician and former Provisional Irish Republican Army (IRA) leader, McGuinness is the MP for the Mid Ulster constituency. Like all Sinn Féin MPs, McGuinness practises abstentionism at Westminster. He is also a member of the Northern Ireland Assembly for the same constituency. Following the St Andrews Agreement and the Assembly election in 2007, he became deputy First Minister of Northern Ireland with Democratic Unionist Party (DUP) leader Ian Paisley as First Minister of Northern Ireland on 8 May 2007. He was re-appointed, with Peter Robinson as First Minister, on 5 June 2008. He served as Minister of Education in the Northern Ireland Executive between 1999 and 2002.

McGuinness joined the IRA around 1970 at the age of 20, after the Troubles broke out. By the start of 1972, at the age of 21, he was second-in-command of the IRA in Derry, a position he held at the time of Bloody Sunday. A claim was made at the Saville Inquiry that McGuinness was responsible for supplying detonators for nail bombs on Bloody Sunday where 14 civil rights marchers were killed by British soldiers in Derry. Paddy Ward claimed he was the leader of the Fianna, the youth wing of the IRA in January 1972. He claimed McGuinness, the second-in-command of the IRA in the city at the time, and another anonymous member gave him bomb parts on the morning of 30 January, the date planned for the civil rights march. He said his organisation intended to attack city-centre premises in Derry on the day when civilians were shot dead by British soldiers. In response McGuinness said the claims were "fantasy", while Gerry O’Hara, a Sinn Féin councillor in Derry stated that he and not Ward was the Fianna leader at the time.