International Women's Day has been celebrated on the 8th March since 1919.

Here are some postage stamps of female mathematicians

Click on a thumbnail to see the full image

International Women's Day China 1953

Maria Agnesi
Italy 2018

Émilie du Châtelet
France 2019

Sophie Germain
France 2016

Caroline Herschel
Guyana 1991

Sofia Kovalevskaya
Russia 1996

Ada Lovelace
France 2022

Florence Nightingale
Italy 2020

Mary Somerville
Scotland 2017

For more stamps see THIS LINK.