UN High Commissioner for Human Rights Louise Arbour today confirmed she would leave her post at the end of June.
She urged her successor to speak out against abuses worldwide despite political pressures.
"We have to be out there assisting those whose obligation it is to enforce these rights. This does not make the position of High Commissioner more comfortable, more sheltered from criticism - quite the opposite," she told journalists before confirming her departure to the 47-member UN Human Rights Council.
Ms Arbour's office has representatives in 47 countries and deploys nearly 400 human rights monitors in UN peacekeeping missions in hot spots such as the Democratic Republic of Congo.
UN Secretary-General Ban Ki-moon has to appoint Ms Arbour's successor, and the UN General Assembly must endorse his choice.
Ms Arbour's candour aroused criticism from around the world, but she brushed this off as "inevitable".
"I tend to distinguish between criticisms that have a certain validity to them, especially those expressed in good faith, and those which often don't have much merit," said Ms Arbour, a former Canadian supreme court justice and chief UN war crimes prosecutor.
"I am not leaving my job because of these pressures. On the contrary, I have to resist the temptation to stay on to face them," she said.
"It is very much for personal reasons. I am not prepared to make a commitment for another four years of this work. . . . I'm going home, basically."