Second-wave feminism was a period of feminist activity that began in the early 1960s and lasted roughly two decades, ending with the feminist sex wars in the early 1980s and being replaced by third-wave feminism in the early 1990s. It occurred throughout the Western world and aimed to increase women's equality by building on the feminist gains of the late 19th and early 20th centuries.

Second-wave feminism built on first-wave feminism and broadened the scope of debate to include a wider range of issues: sexuality, family, domesticity, the workplace, reproductive rights, de facto inequalities, and official legal inequalities. First-wave feminism typically advocated for formal equality and second-wave feminism advocated for substantive equality. It was a movement focused on critiquing patriarchal or male-dominated institutions and cultural practices throughout society. Second-wave feminism also brought attention to issues of domestic violence and marital rape, created rape crisis centers and women's shelters, and brought about changes in custody law and divorce law. Feminist-owned bookstores, credit unions, and restaurants were among the key meeting spaces and economic engines of the movement.

Because white feminists' voices have dominated the narrative from the early days of the movement, typical narratives of second-wave feminism focus on the sexism encountered by white middle- and upper-class women, with the absence of black and other racialized women and the experience of working-class women, although black women wrote and founded feminist publications and political activist groups throughout the movement, especially in the 1970s. At the same time, some narratives present a perspective that focuses on events in the United States to the exclusion of the experiences of other countries. Writers like Audre Lorde argued that this homogenized vision of "sisterhood" could not lead to real change because it ignored factors of one's identity such as race, sexuality, age, and class. The term "intersectionality" was coined in 1989 by Kimberlé Crenshaw at the end of the second wave. Many scholars believe that the beginning of third wave feminism was due to the problems of the second wave, rather than just another movement.

The second wave of feminism in the United States came as a delayed reaction against the renewed domesticity of women after World War II: the late 1940s post-war boom, which was an era characterized by an unprecedented economic growth, a baby boom, a move to family-oriented suburbs and the ideal of companionate marriages. During this time, women did not tend to seek employment due to their engagement with domestic and household duties, which was seen as their primary duty but often left them isolated within the home and estranged from politics, economics, and law making. This life was clearly illustrated by the media of the time; for example television shows such as Father Knows Best and Leave It to Beaver idealized domesticity.

Some important events laid the groundwork for the second wave, specifically the work of French writer Simone de Beauvoir in the 1940s where she examined the notion of women being perceived as "other" in the patriarchal society. Simone de Beauvoir was an existentialist, meaning she believed in the existence of the individual person as a free and responsible agent determining their own development through acts of the will. She went on to conclude in her 1949 treatise The Second Sex that male-centered ideology was being accepted as a norm and enforced by the ongoing development of myths, and that the fact that women are capable of getting pregnant, lactating, and menstruating is in no way a valid cause or explanation to place them as the "second sex". This book was translated from French to English (with some of its text excised) and published in America in 1953.

In 1960, the Food and Drug Administration approved the combined oral contraceptive pill, which was made available in 1961. This made it easier for women to have careers without having to leave due to unexpectedly becoming pregnant. It also meant young couples would not be routinely forced into unwanted marriages due to accidental pregnancies.

Though it is widely accepted that the movement lasted from the 1960s into the early 1980s, the exact years of the movement are more difficult to pinpoint and are often disputed. The movement is usually believed to have begun in 1963, when Betty Friedan published The Feminine Mystique, and President John F. Kennedy's Presidential Commission on the Status of Women released its report on gender inequality.

The administration of President Kennedy made women's rights a key issue of the New Frontier, and named women (such as Esther Peterson) to many high-ranking posts in his administration. Kennedy also established a Presidential Commission on the Status of Women, chaired by Eleanor Roosevelt and comprising cabinet officials (including Peterson and Attorney General Robert F. Kennedy), senators, representatives, businesspeople, psychologists, sociologists, professors, activists, and public servants. The report recommended changing this inequality by providing paid maternity leave, greater access to education, and help with child care to women. However, the extent of Kennedy's support for women's rights has been disputed, with some alleging that a major factor in his support included his efforts to cover up his own womanizing ways. His wife Jackie was also known for presenting herself as a traditional wife, including in the time after Friedan published The Feminine Mystique.