Pillay an acting judge on South Africa's high court since 1996, was named to the post by U.N. Secretary-General Ban Ki-Moon after her nomination was approved by the General Assembly, the United Nations said in a news release.

Since 2003, she has been a judge on the International Criminal Court. In 1999, she was elected Judge President of the International Criminal Tribunal for Rwanda, which she joined in 1995.

Pillay was the first woman to start a law practice in South Africa's Natal Province, providing legal defense services for opponents of apartheid, the United Nations said. She is co-founded Equality Now, an international women's rights organization in New York, and co-founded the Advice Desk for the Abused, as well as ran a shelter for victims of domestic violence.

Pillay, who replaces Louise Arbour, has a bachelor of arts and a bachelor of laws from Natal University South Africa. She earned her law degree from Harvard University.