Nadia Murad, who is also a Nobel Peace Prize nominee, will become the UNODC Goodwill Ambassador for the Dignity of Survivors of Human Trafficking.
Her "appointment marks the first time a survivor of atrocities is bestowed with this distinction," the UN said.
Ms Murad was captured in Iraq in 2014. Six of her brothers were murdered.
The 23-year-old told the BBC she had also been subjected to sexual and physical abuse.
"Under their rule, a captured woman becomes a spoils of war if she is caught trying to escape. She is put in a cell and raped by all the men in that compound. I was gang-raped."
She said she had been bought and sold several times by the militant group. She, however, managed to escape.
Since her escape, she has been advocating for the end of human trafficking.
Ms Murad's ambassadorship "will focus on advocacy initiatives and raise awareness around the plight of the countless victims of trafficking in persons, especially refugees, women and girls," the UN said.
Her induction ceremony at the UN will be witnessed by Secretary-General Ban Ki-moon, US Ambassador Samantha Power and attorney for Ms Murad, Amal Clooney.
A young Yazidi woman who survived trafficking and gang-rape by so-called Islamic State militants is to be appointed a UN ambassador.