Cora Weiss, active for more than half a century in support of gender equality, international peace, the anti-Vietnam War movement, civil rights and nuclear disarmament, and who helped organize some of the important mass demonstrations of the 1960s, died on Dec. 8 in Manhattan. She was 91.

In 196`1, when she was raising her children in the Riverdale neighborhood of the Bronx, she heard about Women Strike for Peace, a new group organizing demonstrations against nuclear weapons testing. She joined.

“In my experience with Women Strike for Peace, we got things done,” she said. Within a few years, Ms. Weiss had become co-chairwoman of the New Mobilization Committee to End the War in Vietnam and had helped organize one of the largest antiwar protests in the United States.

A lifelong supporter of the United Nations, Ms. Weiss was particularly proud of her work in helping to draft United Nations Security Council Resolution 1325, which affirmed the importance of the role of women in the peace process and protecting their security, unanimously adopted in 2000.

Later in life, as president of the Hague Appeal for Peace, she became involved in global peace education. “I’ve decided that it’s the only sustainable thing,” Ms. Weiss said. “You can march, you can protest, you can make phone calls, you can write letters. But education is the closest thing, I think, to a sustainable form of social change.”