Charlize Theron, Oprah Winfrey and Mary J. Blige are among the stars calling for gender equality around the world.
An open letter written to world leaders, organised by the ONE Campaign ahead of International Women's Day on Tuesday (08Mar16), was released on Sunday.
It highlights the fact that 155 countries have laws that discriminate against women, while 500 million women worldwide can't read and 62 million young girls around the globe are denied the right to education.
"Nowhere on earth do women have as many opportunities as men. Nowhere," the letter reads. "While the debate around this truth rages everywhere, girls and women living in extreme poverty - those often hardest hit by the injustice of gender inequality - have been left out of the conversation.
"This must change. The fight for gender equity is global."
Sir Elton John, Tina Fey, Amy Poehler, Colin Farrell, Robert Redford, Shonda Rhimes, Ashley Judd, Danai Gurira, Connie Britton, Patricia Arquette, Muhammad Ali, Sheryl Sandberg and Sean Parker all signed the letter.
The letter accompanies a report from the ONE Campaign, co-founded by U2 rocker Bono, which found that west Africa's Niger had topped their list of the countries it's the "toughest" to be born a girl.
According to the report, entitled Poverty Is Sexist, females in the country have significantly less rights that their male counterparts, including being unable to open their own bank accounts.
One of the main issues highlighted in the letter is that more funding is needed to help women fight HIV and malnutrition. These pleas come ahead two major summits that will be taking place this year - Nutrition For Growth and Global Fund.
"The British Government have been at the forefront of efforts to put girls and women at the heart of international development and they should seize the opportunities of this year's major summits to cement this record," Diane Sheard, the UK director of the ONE Campaign, said in a statement.
"As hosts of the first Nutrition For Growth summit and major historical contributors to the Global Fund, now is not the time for the UK to take a back seat."