Third-wave feminism is a feminist movement that began in the early 1990s; it was prominent in the decades prior to the fourth wave. Grounded in the civil-rights advances of the second wave, Gen X third-wave feminists born in the 1960s and 1970s embraced diversity and individualism in women, and sought to redefine what it meant to be a feminist. The third wave saw the emergence of new feminist currents and theories, such as intersectionality, sex positivity, vegetarian ecofeminism, transfeminism, and postmodern feminism. According to feminist scholar Elizabeth Evans, the "confusion surrounding what constitutes third-wave feminism is in some respects its defining feature."

The third wave is traced to Anita Hill's televised testimony in 1991 to an all-male all-white Senate Judiciary Committee that the judge Clarence Thomas had sexually harassed her. The term third wave is credited to Rebecca Walker, who responded to Thomas' appointment to the Supreme Court with an article in Ms. magazine, "Becoming the Third Wave" (1992). She wrote:

So I write this as a plea to all women, especially women of my generation: Let Thomas' confirmation serve to remind you, as it did me, that the fight is far from over. Let this dismissal of a woman's experience move you to anger. Turn that outrage into political power. Do not vote for them unless they work for us. Do not have sex with them, do not break bread with them, do not nurture them if they don't prioritize our freedom to control our bodies and our lives. I am not a post-feminism feminist. I am the Third Wave.

Walker sought to establish that third-wave feminism was not just a reaction but a movement in itself because the feminist cause had more work ahead. The term intersectionality to describe the idea that women experience "layers of oppression" caused, for example, by gender, race, and class had been introduced by Kimberlé Crenshaw in 1989, and it was during the third wave that the concept flourished.

In addition, third-wave feminism is traced to the emergence of the riot grrrl feminist punk subculture in Olympia, Washington, in the early 1990s. As feminists came online in the late 1990s and early 2000s and reached a global audience with blogs and e-zines, they broadened their goals, focusing on abolishing gender-role stereotypes and expanding feminism to include women with diverse racial and cultural identities.

The rights and programs gained by feminists of the second wave served as a foundation for the third wave. The gains included Title IX (equal access to education), public discussion about the abuse and rape of women, access to contraception and other reproductive services (including the legalization of abortion), the creation and enforcement of sexual-harassment policies for women in the workplace, the creation of domestic-abuse shelters for women and children, child-care services, educational funding for young women, and women's studies programs.

Feminists of color such as Gloria E. Anzaldúa, bell hooks, Cherríe Moraga, Audre Lorde, Maxine Hong Kingston, Leslie Marmon Silko and the members of the Combahee River Collective sought to negotiate a space within feminist thought for consideration of race. Cherríe Moraga and Gloria E. Anzaldúa had published the anthology This Bridge Called My Back (1981), which, along with All the Women Are White, All the Blacks Are Men, But Some of Us Are Brave (1982), edited by Akasha (Gloria T.) Hull, Patricia Bell-Scott, and Barbara Smith, argued that second-wave feminism had focused primarily on the problems of white women. The emphasis on the intersection between race and gender became increasingly prominent. However, allowing third wave feminism to adopt the paradigm of intersectionality can erase the narrative of second-wave feminist of color who worked towards inclusion.

In the late 1970s and early 1980s, the feminist sex wars arose as a reaction against the radical feminism of the second wave and its views on sexuality, countering with a concept of "sex-positivity", and heralding the third wave.