Caoimhghín Ó Caoláin (born 1953) is an Irish Sinn Féin politician. He has been a TD for Cavan Monaghan since 1997 and is currently the Parliamentary Leader of Sinn Féin in Dáil Éireann.

Caoimhghín Ó Caoláin was born in Monaghan in 1953. He has been active in Irish Republican circles for a number of years. He was Director of Elections in the H-Block campaign of 1981 when Kieran Doherty was elected TD for the Cavan Monaghan constituency. Between 1982 and 1985 he was General Manager of the republican newspaper An Phoblacht. Ó Caoláin's first political success came in 1985 when he was elected to Monaghan County Council as a Sinn Féin councillor.

Ó Caoláin represented Sinn Féin at the Forum for Peace and Reconciliation in Dublin in the mid-nineties and was also a member of the Sinn Féin negotiations team during the talks which led to the Good Friday Agreement in 1998. In 1997 he was elected to Dáil Éireann for the first time as a TD for Cavan Monaghan, becoming the first modern Sinn Féin Teachta Dála. He was subsequently re-elected in 2002. At the last general election he was joined by four other Sinn Féin deputies. Ó Caoláin is currently Sinn Féin's Parliamentary Group Leader in the Dáil and is also spokesperson on the Peace Process and the Six Counties (i.e Northern Ireland). He is also has party spokesperson for Finance and Health & Children.