The Treaty on the Prohibition of Nuclear Weapons will come into force on January 22nd.
The announcement comes after Honduras became the 50th nation to ratify what the UN says is an "historic" agreement.
The document bans the development, production, testing, storing, using or threats to use nuclear weapons.
However, none of the world's major nuclear powers, the US, Britain, France, China or Russia, have signed it.
Today, the 50th ratification to the Treaty on the Prohibition of Nuclear Weapons was deposited with the Secretary-General.
This is a meaningful commitment towards the total elimination of nuclear weapons, the highest disarmament priority of the @UN. https://t.co/tCB3gcjTJh— UN Spokesperson (@UN_Spokesperson) October 25, 2020
The Minister for Foreign Affair Simon Coveney said the treaty adds "fresh momentum" to achieving the goal of a nuclear-weapons-free world.
He said: "At a time of rising international tensions, and as we see renewed concerns about nuclear weapons proliferation, a renewed arms race and the destabilising effects of technological developments, the support for the Treaty is a clear indication of the will of the majority of countries to add fresh momentum to achieve the goal of a world free of nuclear weapons.
"The significance of the Treaty lies in the fact that for the first time, the core objective of the prohibition of nuclear weapons will be clearly and unambiguously stated in an international Treaty.
"It challenges us to think about the enormity of the threat posed by these weapons, and by stigmatising and prohibiting nuclear weapons, it makes a statement that these weapons are no longer acceptable.
He added: "I am pleased that Ireland ratified the Treaty earlier this year, on the 75th anniversary of the bombing of Hiroshima, continuing our long history of leadership in nuclear disarmament.
"On this occasion, I pay particular tribute to all victims and survivors of nuclear weapons use and nuclear weapons testing.
"We owe a debt of gratitude to the survivors who have spent decades campaigning for the elimination of nuclear weapons."
