Griffiths was appointed by Secretary-General Antonio Guterres as the UN's new Yemen envoy Friday, replacing Mauritania's Esmail Ould Shaikh Ahmad who struggled to end the conflict.
Officials hope he would bring fresh impetus to the peace and humanitarian process when he takes over from Ismail Ould Cheikh Ahmed, of Mauritania, whose term ends this month after almost three years in the role.
"Mr Griffiths brings extensive experience in conflict resolution, negotiation, mediation and humanitarian affairs", United Nations spokesman Stephane Dujarric said on Friday.
A Saudi Arabia-led coalition intervened in Yemen's civil war in 2015, backing government forces fighting Iran-allied Houthi rebels.
His predecessor, Jamal Benomar, also quit after four years of efforts to establish a political transition fell apart. He held that position from 1999 to 2010.
He has also worked in the British diplomatic service and for worldwide agencies, such as UNICEF and the non-governmental organization Save the Children.
Griffiths faces challenging waters ahead.
In 1994, he served in Geneva as the director of the Department of Humanitarian Affairs, which preceded the establishment of the UN Office for the Coordination of Humanitarian Affairs.