Zimbabwe's highest court on Wednesday outlawed marriages of girls under 18, striking off legislation which had allowed girls as young as 16 to marry with parental consent.
In practice, girls as young as 12 have been reported to marry in the southern African country.
One-third of girls marry before the age of 18, said Tendai Biti, one of the human rights lawyers who asked the Constitutional Court to change the legislation.
"Under the age of 18, male or female may not enter into marriage, whether unregistered, customary or religious," said Vernanda Ziyambi, one of the nine judges who unanimously adopted the ruling.
For males, the legal age of marriage had already been 18.
Biti and other lawyers represented two women who had married at ages 13 and 15 and who did not want other women to suffer a similar fate. "We now wait for parliament to come with stiff penalties to ensure that this ruling is safeguarded and enforced," Biti said.
But the ruling was expected to face resistance especially in the countryside, where many poor parents marry off their under-age daughters in order not to have to support them financially and to obtain a payment.