Sinn Fein's Michelle O'Neill has described her appointment as the party's new Stormont leader as the biggest honour and privilege of her life.
The Mid Ulster Assembly member told party faithful that by succeeding Martin McGuinness she was following in the footsteps of a "political giant".
"No-one can replace Martin but what I can do is to continue his good work to unite our people and to unite our country," she said.
The 40-year-old mother-of-two, from Clonoe, Co Tyrone, takes over as Sinn Fein's figurehead north of the Irish border weeks before a snap Assembly election.
Mr McGuinness's resignation as deputy first minister in protest at the Democratic Unionists' handling of a botched green energy scheme triggered the collapse of the powersharing administration.
The Sinn Fein veteran later announced that he would not seek re-election due to his ongoing battle against a serious illness.
Mr McGuinness was joined by party president Gerry Adams and vice-president Mary Lou McDonald at an event at Parliament Buildings, Belfast, to confirm the appointment of the hotly-tipped Ms O'Neill, Sinn Fein's current health minister at Stormont.
"For me to be selected to lead our party in the north is truly the biggest honour and privilege of my life," she said, as her son Ryan, daughter Saoirse and mother Kathleen looked on.
"I feel an enormous responsibility on my shoulders and, while I don't under-estimate my task given the changing political world - locally, nationally and internationally - I will not let you down."
Mr Adams said Ms O'Neill represented a "new generation" for the party.
"As a united all-Ireland team, we will give her the space and support to find her own voice and continue the good work Martin pioneered," he said.
Mr McGuinness delivered his own take on a familiar republican slogan, which Mr Adams once used in reference to the IRA, to insist he would still be involved in political activism for the party.
"I haven't gone away, you know," he said, to cheers and applause from supporters gathered in the Long Gallery of the historic building.
The former deputy first minister hailed his successor as a "people's politician".
"Change happens and we are now witnessing big change today," he said.
Mr McGuinness said she had proved her fortitude and credentials when facing down anti-peace process elements within republicanism in Co Tyrone.
"She refused to be intimated and continued to build support for Sinn Fein," he said.
"I knew she was made of strong stuff.
"I knew this was a woman, even in the very early days, of great ability."