The Constitution of Ireland is the fundamental law of Ireland. It asserts the national sovereignty of the Irish people. The constitution is broadly within the tradition of liberal democracy, being based on a system of representative democracy. It guarantees certain fundamental rights, along with a popularly elected non-executive president, a bicameral parliament, a separation of powers and judicial review.

It is the second constitution of the Irish state since independence, replacing the 1922 Constitution of the Irish Free State. It came into force on 29 December 1937 following a statewide plebiscite held on 1 July 1937. The Constitution may be amended solely by a national referendum. It is the longest continually operating republican constitution within the European Union