16 Days of Activism Against Gender-Based Violence is an international campaign to challenge violence against women and girls. The campaign runs every year from 25 November, the International Day for the Elimination of Violence against Women, to 10 December, Human Rights Day. It was initiated in 1991 by the first Women's Global Leadership Institute, held by the Center for Women's Global Leadership (CWGL) at Rutgers University.

Based on this passage, when does the 16 days of activism campaign start? Let's think fast. Stream of consciousness:
To answer this question, we should know that: The campaign runs every year from 25 November, the International Day for the Elimination of Violence against Women, to 10 December, Human Rights Day. So the final answer is 25 November , the International Day for the Elimination of Violence against Women.