Oprah Winfrey, Meryl Streep and Chadwick Boseman are among several stars putting world leaders "on notice", demanding gender equality across the globe.
In an open letter, backed by actors such as Reese Witherspoon, Michael Sheen and Thandie Newton, they call for a commitment to help every girl get an education.
The letter, led by the ONE Campaign, highlights inequality between men and women, particularly in some of the poorest countries in the world.
Amy Schumer, Chelsea Clinton and Ryan Reynolds are also among the 140 high-profile names backing the letter.
"Dear World Leaders, we're putting you on notice," it reads.
"For 130 million girls without an education. For one billion women without access to a bank account. For 39,000 girls who became child brides today. For women everywhere paid less than a man for the same work.
"There is nowhere on earth where women have the same opportunities as men, but the gender gap is wider for women living in poverty.
"Poverty is sexist. And we won't stand by while the poorest women are overlooked.
"You have the power to deliver historic changes for women this year. From the G7 to the G20; from the African Union to your annual budgets; we will push you for commitments and hold you to account for them. And, if you deliver, we will be the first to champion your progress.
"We won't stop until there is justice for women and girls everywhere. Because none of us are equal until all of us are equal."
One of the signatories, Nashville actress Connie Britton spoke in the wake of the Time's Up movement against sexual harassment.
She said: "We have seen an astounding level of attention paid to the harmful impacts that sexism and systemic gender inequality have on our society.
"We must do more to lift up and empower those who are most overlooked, so that every girl and woman has access to an education and to the same opportunities as their fellow brothers.
"This year, it is my hope that all of us, especially our leaders, join in the fight for full equality."
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The UK director of the ONE Campaign said girls' education was "essential" in the fight to end poverty.
Romilly Greenhill said: "Until we're able to break down the barriers holding girls and women back on a global level, extreme poverty and gender inequality will continue to exist."