Women activists commemorate November 25th as a day against violence against women in honor of the Mirabal sisters, three political activists from the Dominican Republic who, on orders of the Dominican ruler, Rafael Trujillo, were brutally assassinated in 1960. On this day every year, from the 25th November till the 10th December, women’s organizations involving thousands of participants worldwide start campaigning for, '16 Days of Activism against Gender Violence'. (The last day of the campaign coincides with the International Human Rights Day).

Statistics show that one in three women in the world are coerced into sex, experience violence and abuse in their lifetime, and that the abuser is usually someone well known to them, such as a friend of the family or relative. Violence against women and girls is a widespread and universal problem. Perhaps the most pervasive human rights violation that we know today, it devastates lives, fractures communities, and stalls development.

In 1999, the UN joined the campaign by designating November 25th the International Day for the Elimination of Violence against Women, inviting governments, international organizations and NGOs to organize activities designed to raise public awareness of this universal problem.

You can look at the documents below for more specific and comprehensive information:
CEDAW, The Convention on the Elimination of All Forms of Discrimination against Women (adopted in 1979 by the UN General Assembly)
http://www.un.org/womenwatch/daw/cedaw/
Declaration on the Elimination of Violence against Women (adopted in 1993 by the UN General Assembly)
http://www.un.org/documents/ga/res/48/a48r104.htm