The female author known for her feminist classic "The Second Sex" is Simone de Beauvoir. Published in 1949, this seminal work challenged the societal norms and pressures placed on women. De Beauvoir explored the concept of otherness and the structures that perpetuated patriarchy. She argued for women’s liberation and the necessity of equality, asserting that one is not born a woman but becomes one through cultural and social conditioning. Her work has been instrumental in shaping feminist theory and continues to influence discussions on gender and equality today.