Gerry Adams is stepping down after more than 34 years as the party's president
Mary Lou McDonald has been officially elected as the new leader of Sinn Féin.
The Dublin Central TD will replace Gerry Adams, who steps down as party president after more than 34 years.
Deputy McDonald was the only candidate nominated for the role, and was named as president-elect last month.
She was officially elected by hundreds of Sinn Féin members at the Ard Fheis at the RDS in Dublin this afternoon.
In an acceptance speech, Deputy McDonald insisted her election was 'not a coronation'.
The new party leader called for a united Ireland, and said Ireland is no longer orange and green but a rainbow of colours.
She stated: "We will not allow those who want to use the past to maintain division and inequality to have their way.
"There is no value in re-fighting the battles of the past - the war is long over".
She also said that the party will campaign in favour of repealing the 8th amendment in the planned referendum, saying: "I trust women. This referendum provides us with an historic opportunity to finally ensure that compassion and trust in women prevails."
Sinn Féin's leader in the North, Michelle O'Neill, was confirmed as the party's deputy leader.
She was also the only candidate nominated for the role.
Ms O'Neill told delegates it's time to look towards the future:
Today's special Ard Fheis in Dublin marked the first time party members have chosen a new leader since 1983.
Pearse Doherty, TD for Donegal South West, paid tribute to the outgoing party president at today's Ard Fheis.
He said: "Gerry [Adams] has for four decades led from the front of the Republican struggle.
"Gerry is respected across Ireland and across the globe as a patriot, as a statesman, and as a peacemaker. Gerry Adams stands heads and shoulders above any other contemporary Irish political leader."
Gerry Adams has been a divisive figure for many during his decades in Irish politics.
He insists he was never a member of the IRA, but has said he doesn't 'disassociate' himself from the organisation.
Deputy Adams became a key figure in the peace process, and led his party towards increased political prominence in both the North and the Republic.
This week, Mr Adams was asked what he thought his legacy would be, and responded: "God knows. I'm not really interested. Some people say 'what's your legacy?' - I won't be around."
There's only one Gerry A - The foremost political leader of his generation. My mentor and friend. pic.twitter.com/ITFMi1ZUYx— Mary Lou McDonald (@MaryLouMcDonald) February 9, 2018
For most of his first 10 years in charge Sinn Féin was banned from the airwaves, but it is now a very different picture for the party.
In 1997 they had just one Dáil seat, and now they hold 23 - Mary Lou McDonald is taking over as the leader of the third most popular party in the Dáil.
Deputy McDonald has made her name with a series of strong performances in Leinster House, such as her critique of Transport Minister Shane Ross during last year's Bus Éireann strike.
However, she will have a number of issues to overcome - such as persistent allegations of bullying within the party; the lack of any substantial progress on restoring the Northern Ireland Executive; and how to broaden support to get into government in the south.
Reporting by Sean Defoe and Stephen McNeice