The Betfred Women's Super League will expand to 10 teams in 2020 with the addition of Huddersfield and Warrington.
It will be the third consecutive year of expansion since the WSL was launched by the Rugby Football League in 2017 with just four teams.
Huddersfield and Warrington both entered the Women's Rugby League Championship for the first time in 2019 and have been granted Super League membership for 2020 and 2021.
Thomas Brindle, the RFL's head of growth, said: "This is another positive step in the Betfred Women's Super League success story.
"The expansion to seven clubs in 2018 and eight in 2019 has undoubtedly enhanced the stature of the competition and of women's rugby league.
"We have a significant goal of increasing the number of women and girls playing rugby league to 21,000 by 2021 - when England will host the Women's World Cup alongside Men's and Wheelchair competitions.
"The England team are currently in Papua New Guinea on a groundbreaking tour, which is an important part of their World Cup preparations following their appearance in the World Cup Nines in Sydney last month."