Sinn Fein President Mary Lou McDonald has proclaimed that "the orange state is gone and it's not coming back" at an event to mark the anniversary of the first Dail in Dublin.
Mrs McDonald and party representatives met in Mansion House to celebrate 100 years since the meeting of the First Dail at the venue on January 21 1919.
The Sinn Fein leader also said that Brexit and world politics were driving events "towards the logic of Irish unity".
She used the 100th anniversary event to reaffirm her party's commitment to working for a united Ireland and set their sights on government in both Northern Ireland and the Republic.
Mrs McDonald said the Good Friday Agreement had guaranteed a "a historic opportunity to build a United Ireland by peaceful, democratic means".
"Let us build a genuine people's campaign for a United Ireland based on progressive demands for a better and fairer society for all," she said.
"We have an opportunity during this time of political, constitutional and social transition to fix the broken, two-state system and eradicate the social and economic ills that it has created.
"With the support of the people we have ensured that the Orange State is gone and it's not coming back."
The Sinn Fein President said her party would pursue "vigorously the democratic imperative of a United Ireland".
She told the event that the "final chapter in Irish Unity" was approaching.
"Our focus now is on building Sinn Fein to be the biggest party on this island, acting as the major catalyst for political, economic and social progress and with the ability to lead a radical Republican government," Mrs McDonald said.
"And let me be very clear here today that the Sinn Fein leadership of 2019 is as determined to achieve the objectives of the First Dáil as those who gathered in this place one hundred years ago.
"We must dare to win, we must plan to win and we must act to win. And let me tell you we will win. We will have a new and united Ireland.
"We will return to this place and we will remember all those who came before and we will celebrate an Irish Republic of equal citizens."