Mary Lou McDonald will succeed Gerry Adams as Sinn Fein leader, the party said on Saturday, completing a generational shift for the Irish nationalist party as it bids to enter government on both sides of the Irish border.
The politician (48) was the only candidate proposed to replace Adams as the deadline for other candidates to put their names forward expired yesterday evening.
Ms McDonald will be formally ratified at a special Sinn Féin Ard Fheis in Dublin.
The party's deputy leader and Dublin Central TD was announced as president-elect at a Sinn Féin AGM in Belfast this morning, a day after nominations for the leadership closed.
In Belfast, Mr Adams said: "We need to have a party that's fit for objective, we need to have a plan".
"So if you didn't get a nomination and wanted this job it's too late now".
Sinn Fein is now the third biggest party in the Republic of Ireland and the second biggest party in Northern Ireland.
Who is Mary Lou McDonald?
In Belfast, Mr Adams, the Sinn Fein party president for three decades, said: 'We need to have a party that's fit for objective, we need to have a plan.
With the big two parties likely to be able to form another minority government at best at elections that could come as soon as this year, McDonald's leadership could also make Sinn Fein a more palatable coalition partner.
Ms McDonald's judgment was called into question by political opponents following her response to the controversy caused by former Sinn Féin MP Barry McElduff's offensive social media post about the Kingsmill massacre.
Mr Adams added: "We have to challenge ourselves and our support base".
"For us in Sinn Fein in the time ahead, we have to grow our party, not just our mandate but also our capacities".
"Standing still is not an option. That will benefit all sections of our people".