Rachel Katznelson (later Shazar) was born in 1885 (or possibly 1888) in the city of Babruysk, then in the Russian Empire, to a traditional Jewish family.

This gave her the possibility of going to university, which was only open to a small percentage of the Jewish community.

In 1916, she was elected to the first Cultural Committee of the Labor Movement, alongside Berl Katznelson and Yitzhak Tabenkin (both also originally from Babruysk), and worked with them to enhance the education of workers.

She was later elected as a member of the cultural committee of the Achdut Ha'avodah party and, in 1924, of the Histadrut.

Throughout her life, she was actively involved with the Histadrut and the Mapai party, and performed many public duties.