Gerry Adams will today step down as leader of Sinn Fein after more than 34 years in the post.
Dublin Central TD Mary Lou McDonald will officially replace Mr Adams at a special party conference in the RDS in Dublin this afternoon (Saturday).
Mrs McDonald was the sole nominee to take over the reigns of the republican party.
Around 2,000 delegates are expected to gather at the conference for the ratification of Mrs McDonald as the next party president.
Mrs McDonald has been a TD for Dublin Central since 2011.
Before getting elected to the Dail (parliament), she was an MEP representing the Dublin constituency - becoming Sinn Fein's first MEP in the Republic of Ireland in 2004.
In January when she was announced as president-elect Mrs McDonald said that under her leadership the party would aim to convince unionists that a United Ireland was the best way forward for everyone.
She said her leadership would mark a defining chapter in the achievement of a United Ireland.
Sinn Fein's Northern Ireland leader Michelle O'Neill will also be proposed for the vice-president position at today's conference.
Mr Adams announced in November that he was stepping down after more than three decades.
The move marks a historic shift in the political landscape in both Northern Ireland and the Republic.