Northern Irish peace activist who, with Mairéad Corrigan (Corrigan-Maguire, Mairéad), founded the Community for Peace People in 1976 and with her shared the 1976 Nobel Prize for Peace.

Williams, an office worker and wife and mother, took little part in public life until August 1976, when she witnessed an incident that moved her to speak out. An Irish Republican Army terrorist was shot by British troops while fleeing in a car; the car went out of control and struck several people, killing three children. Williams immediately began circulating petitions in Protestant neighbourhoods calling for an end to sectarian violence. This activity soon brought her into association with Mairéad Corrigan, an aunt of the slain children, who had been similarly galvanized into action. Together they founded the Community for Peace People to provide services for victims of the Northern Ireland conflict.

In 1978 Williams and Corrigan resigned their positions of leadership in the Community and by 1980 had become estranged. In 1982 Williams married and moved to Florida in the United States.