Simone de Beauvoir was born and raised in Paris at the beginning of the 20th century. Her parents were originally wealthy, but struggled somewhat after the first world war. She was raised Catholic by a religious mother and even grew up wanting to be a nun, though she became an atheist in her adolescence and went on to reject religion in her adult life. de Beauvoir was lucky to also be raised by a father who believed in educating her, despite the fact that she was a woman and lived in a time when this was uncommon. She was thus enthusiastic about intellectual pursuits from an early age, and went on to apply this enthusiasm at a private Catholic school, and later at the University of Paris. In university, she focused her studies on philosophy. She went on to complete her studies at the Sorbonne, focusing on philosophy, Greek, logic, and psychology. In particular, she studied the mathematician and philosopher Gottfried Wilhelm Liebniz. While at university, de Beauvoir studied alongside other philosophers who rose to prominence in her time, such as Paul Nizan, Jean Hyppolite, and Jean-Paul Sartre.
Famously, Simone de Beauvoir received second place in a competitive philosophy exam that Sartre won. It is less well known that, unlike Sartre and the other top students who sat for the exam, she was never an official student at the university that administered the test, but rather sat in on classes and studied independently. She and Sartre would go on to maintain a lifelong relationship and exchanged many ideas with one another. Sartre's contributions to existentialism would also go on to shape de Beauvoir's thinking about feminism and philosophy in general. However, she and Sartre are also well known for keeping an open relationship. de Beauvoir rejected marriage on principle, and insisted that, although their partnership was central to both of their lives, she and Sartre maintain other love affairs over time. She was attracted to both men and women, and is notorious for her romantic exploits. Some of these are discussed in her semi-autobiographical fiction, such as the 1954 novel The Mandarins, which won the famous Prix Goncourt.
Simone de Beauvoir actually rejected being labeled a philosopher and wanted to be known as an author above all. Nevertheless, her feminist text The Second Sex is one of her best-known works. Published in 1949, it lays out her philosophy regarding feminist theory. It is well known for establishing some of the key ideas of second wave feminism. Much of this text is shaped by Sartre's existentialist philosophy, which gave de Beauvoir the idea of an Other vs a self as a framework for understanding gender relations.
de Beauvoir and Sartre were major figures in the French intellectual scene of the mid-20th century. As such, they were important voices during World War II and the Algerian War of Independence, two major conflicts that defined French political and cultural life in the 20th century. During World War II, she and Sartre were not a major part of the French resistance to Nazism, but they did contribute a leftist journal in which they commented on events of the time. de Beauvoir Sartre, and other intellectuals of the time were known for supporting socialism, which became more complicated over time as the horrors of Russian gulags and other abuses of authority came to light. de Beauvoir herself would go on to champion other social justice movements over time, such as the plight of Algerians in France and the feminist cause.