Sophie Germain (1776-1831) is an emblematic example of a woman who produced mathematics in the first third of the nineteenth century. Self-taught, she was recognised for her work in the theory of elasticity and number theory. After some biographical elements, I will focus on her contribution to number theory in the context of the mathematical practices and social positions of the mathematicians of her time. I will then analyse some receptions and uses of Germain's life and scientific work under the French Third Republic.