For millions, it is the time to celebrate the economic, political and social achievements women have made since the first International Women's Day when people marched across Europe for a woman's right to vote, work and hold public office.
For ActionAid, International Women's Day is also a time to shine a spotlight on the struggles women face now in the developing world and to build solidarity to tackle the urgent challenges ahead. ActionAid campaigns for a world where women and men, girls and boys, have equally good chances in life, free from want and free from fear.
Get Lippy.... ActionAid asked the celebrities to send a message of support to the millions of women in the developing world who are struggling everyday to improve their lives.
Since ActionAid believes that more unites women than divides them, the charity also asked the celebrities to say what they thought was the best and worst thing about being a woman today.
You can see what they had to say at https://www.youtube.com/watch?v=YynQrIxFHEQ and you can also GET LIPPY and send your messages to: www.actionaid.org.uk/iwd