Ayesha Malik, 55, has been sworn in as Pakistan's first female Supreme Court in the capital Islamabad. She sits on a bench with 16 other male colleagues in the country's top court.
Lawyers and activists have names it a rare victory after decades of struggle to get representation for women in Pakistan's male-dominated society.
Her appointment was opposed by some lawyers and judges citing her as less senior to other candidates.
The country’s judiciary has remained historically conservative and male-dominated, the only South Asian country to have never had a female Supreme Court judge. In addition, only 4% of Pakistan's high court judges are women.
Justice Malik, educated at the Pakistan College of Law and Harvard University, has served as a high court judge in the city of Lahore in eastern Pakistan for the last two decades.
"It's a huge step forward," rights activist and lawyer Nighat Dad told AFP news agency. "It is history in the making for Pakistan's judiciary."
Justice Malik is the fourth most senior judge in the lower court from which she has now been elevated.