A proposal to repeal Article 522 of the penal code -- which deals with rape, assault, kidnapping and forced marriage -- was introduced last year and approved by a parliamentary committee in February.
On Wednesday, it was ratified by the full parliament, the official National News Agency and activist group ABAAD said.
"Congratulations to women in Lebanon," the NGO wrote in a statement on its Facebook page.
"Today's win is a victory for the dignity of women," it added.
"It is no longer possible to escape punishment for rape and sexual acts carried out by force and coercion," said the group, which has spearheaded the campaign to repeal the much-reviled article.
The article, which also dealt with the rape of minors, allowed for the perpetrator of sexual assault to avoid prosecution by marrying their victim.
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There are no precise figures on how many rapists marry their victims to avoid punishment, but activists say the practice mainly took place in rural areas.
Danielle al-Hweik, a lawyer with ABAAD, hailed the ruling as the result of pressure from activists, but said there would be new battles ahead.
"There are many other issues that we're working on," she told AFP.
"We remain concerned by other articles."
Among the legal provisions rights groups want repealed are articles that allow a person accused of "consensual" sexual relations with a minor under 15 to avoid sanction by marrying the minor.
Lebanon's decision comes just over two weeks after Jordan's parliament binned a similar article in its penal code.
And in July, Tunisia passed legislation doing the same as part of a bill designed to "end all violence against women".