Antonio Guterres, the man formally nominated to be the next UN secretary general, says he plans to "serve the most vulnerable".
The former Portuguese prime minister said he felt both "gratitude and humility" by the appointment.
He said he would serve the "victims of conflicts, of terrorism, rights violations, poverty and injustices of this world".
Mr Guterres was unanimously nominated by the UN Security Council on Thursday.
The UN General Assembly is expected to meet next week to approve his five-year appointment.