Taoiseach Enda Kenny and other European leaders will today sign the Rome Declaration in the Italian capital.
The 27 leaders will be joined by the President of the European Council, the President of the European Commission and the President of the European Parliament.
The Declaration has been negotiated by the Member States and acknowledges the many achievements of the EU, as well as setting out the challenges it faces and the steps that must be taken to confront them.
It will be signed on the 60th anniversary of the Treaty of Rome - the founding European Treaty of what has now become the European Union.
Last night, the leaders had an audience with Pope Francis in the Vatican, who warned that the European Union risks dying without a new vision.