Actress Nicole Kidman will promote women's rights around the world as goodwill ambassador of the United Nations Development Fund (Unifem).
Nicole Kidman filmed inside the UN for The Interpreter
The Australian star will focus on issues such as ending violence against women, the fund said.
Kidman played a UN employee in the movie The Interpreter in 2005.
The 38-year-old was also named Companion in the General Division of the Order of Australia for her charity work and her acting.
The honour comes as her native country celebrates Australia Day on Thursday.
She was recognised for her work towards "health care through contributions to improve medical treatment for women and children and advocacy for cancer research".
Kidman was also cited for her support of young actors through the Australian Theatre for Young People, where she trained as a teenager.
"I am deeply moved that I have been chosen to receive this prestigious award. It is an honour beyond any of my expectations," she said.
"I am grateful for the opportunities that Australia has given me and it has always been a privilege to represent my country wherever and whenever I can."
Kidman has been a goodwill ambassador for the United Nations Children's Fund since 1994.
In her new role with Unifem, Kidman will help promote women's rights and gender equality issues around the world.
She recently starred in the movie The Interpreter, in which she played a character working for the UN and was given rare access to film inside its New York headquarters.