World Rugby's council will be at least one-third female from next year, the global governing body said as it announced a "transformational" change on Thursday.
The move will see the 32-strong council increased to 49 members, with all the 17 new representatives women.
However, a World Rugby statement said this "will not result in any changes to the existing voting rights of unions or regional associations on Council".
As a result, the 10 leading unions who currently have three votes but only two representatives -- Argentina, Australia, England, France, Ireland, Italy, New Zealand, Scotland, South Africa and Wales -- will have the right to an extra councillor provided that representative is female.
Meanwhile, the 2019 men's Rugby World Cup hosts Japan and the six leading regional rugby associations, who currently have two votes but only one representative, now have the right to send an extra representative but again that person must be a woman.
"The reform is historic, reflective of our ambitions and long overdue," said World Rugby chairman Bill Beaumont.
"If we are to promote and nurture the growth of women in rugby then change must be led from the top," the former England captain added, following a recent council meeting in London where the "2015-25 Women's Plan", a global strategy to grow women's rugby union, was also agreed.
Katie Sadleir, World Rugby's general manager of women's rugby, said: "Building on the success of the recent Women's Rugby World Cup in Ireland, the decision to increase the representation of women on Council to more than a third is transformational for rugby.
"It will change the way we govern the sport going forward, making a difference not just for women in rugby but for all of rugby."
Part of that change was evident when World Rugby announced Thursday that Ada Milby, the secretary-general of the Philippine Rugby Football Union, had become the councillor selected under the new procedure following her election by Asia Rugby last weekend.