The victim, Mukhtar Mai, attended Monday's rally in Multan, a major city in the eastern province of Punjab. Waving signs and chanting, the demonstrators, many of them from nearby villages, joined the rally.
Organiser Farzana Bari said more than 3000 women were at the event.
"We will fight for justice for Mukhtar Mai," the women chanted during the rally, while others carried placards reading: "Give protection to Mukhtar Mai."
About 200 police officers observed the demonstration, which ended peacefully.
In June 2002, Mai allegedly was raped by four men on the orders of a village council that wanted to punish her family.
The assault was ordered after Mai's brother was accused of having sex with a woman from a more prominent family, though Mai's family says the allegations were fabricated to cover up a sexual assault against the boy by several men.
Mai, a 33-year-old school teacher, went public to speak about her ordeal, drawing international media attention to crimes against women in Pakistan.
The government pledged to track down her attackers.
A court later sentenced six men to death for Mai's rape. But an appeals court in Multan last Thursday overturned the conviction of five of the men, citing lack of evidence and reduced the other man's sentence to life in prison.
Mai and the government have said they will appeal the ruling in the Supreme Court. She also has expressed fears that the acquitted men might target her for revenge.
Bari said her group, Pattan, a charity working with women in rural communities, will stand by Mai until she gets justice. "We are with every woman who is oppressed and who face injustices," she said.