The acting Environment Minister Alan Kelly has signed the Paris Agreement on climate change at a special ceremony at the United Nations in New York.
The deal was adopted by all 196 Parties to the United Nations Framework Convention on Climate Change in Paris on December 12th last year.
All countries agreed to work together to limit global temperature rise to well below 2°C above pre-industrial levels, and to pursue efforts for a 1.5°C target.
Speaking in New York, Mr Kelly said he is "very proud to represent the Irish people on this very important process having already led the Irish delegation during the negotiations themselves".
"The Paris Agreement represents a major milestone in the collective response to the impacts of climate change and importantly, sends an unequivocal message to business, stakeholders and citizens that all governments are committed to playing their part in addressing the challenges posed by climate change".
Ireland, through the European Union, indicated its commitment through the agreement to reduce greenhouse gas emissions by at least 40% by 2030, compared with 1990 levels.
Discussions on the responsibilities of individual EU member states to meet this commitment are under way and, once agreed, the next step in the implementation of the agreement will be through the ratification process itself.
Today's event is being hosted by UN Secretary-General Ban Ki-moon, and is being held to coincide with Earth Day.
Mr Ban said: "The momentum achieved by so many signatures on one day sends a clear signal of solidarity and resolve. Now we must unleash the full force of human ingenuity and ensure low-emission growth and improved climate resilience".
Robert Glasser, the UN Special Representative for Disaster Risk Reduction, welcomed the fact that so many countries have agreed to sign up to the historic deal - but warned that far more needs to be done to combat climate change.
"We are in real danger of being overtaken by the rapid pace of global warming if signatories do not significantly scale up the level of their ambition to reduce greenhouse gas emissions,” he said.
