The General Assembly, in a plenary meeting, approved Ndiaye's appointment without a vote. She will serve a five-year non-renewable term that begins on Oct. 25, 2019. Ndiaye will succeed Heidi Mendoza of the Philippines.
UN Secretary-General Antonio Guterres on Thursday welcomed the General Assembly's decision, said his press office.
Ndiaye was most recently deputy chief of the UN Children's Fund (UNICEF). Prior to this role, she served as UNICEF's director of internal audit and investigations, and head of the Internal Audit Division of the UN Office of Internal Oversight Services.
The appointment of a UN undersecretary-general needs the approval of the General Assembly, which comprises all UN member states. Undersecretary-generals are the third highest in ranks in the United Nations, after the secretary-general and the deputy secretary-general.