John McGarry (born 1957) is a political scientist from Northern Ireland. He was born in Belfast and grew up in Ballymena, County Antrim. He is currently Professor of Political Studies and Canada Research Chair in Nationalism and Democracy at Queen's University in Kingston, Ontario. He is the author of numerous influential books about the Northern Ireland conflict, many of them co-authored with Brendan O'Leary, whom he met when they both attended Saint MacNissi’s College. McGarry and O'Leary's Policing Northern Ireland: Proposals for a New Start (Blackstaff Press, 1999) is considered to have had a significant influence on the work of the Independent Commission on Policing for Northern Ireland. He currently sits on the advisory council of the Centre for the Study of Democracy and worked as a senior advisor on power-sharing to the United Nations in 2008-09. In addition to teaching, he is currently an advisor on governance to the UN-led negotiations in Cyprus. His contribution and work were recognized in 2010 when he was invested into the Royal Society of Canada. He won Canada's prestigious Trudeau Fellowship Prize in 2011. In 2013, he was awarded the Queen Elizabeth II Diamond Jubilee Medal, and the Killam Prize. The latter is Canada's most prestigious research prize.
McGarry and Brendan O'Leary have long backed consociationalism as a method of conflict management for Northern Ireland, and are supportive of the Good Friday Agreement. In this regard, Arend Lijphart has been a significant influence on their work. In 2009, a book entitled Consociational Theory: McGarry and O'Leary and the Northern Ireland Conflict was published, edited by Rupert Taylor.
McGarry is married to political theorist Margaret Moore, an expert on issues of nationalism and liberalism.