The Irish referendum on the Treaty establishing a Constitution for Europe is a referendum expected to be held on in late 2005 or early 2006 to decide whether the Republic of Ireland should ratify the proposed Constitution of the European Union.

Commentators expect a victory for the 'yes' campaign. The referendum will be legally binding, although it is worth noting that a second referendum was held on the Treaty of Nice after changes were made to the draft treaty when the first vote rejected it by a narrow margin.