Water can be a key trigger of conflict among communities or between citizens and the state. This is happening all over the world: from Iraq to Guatemala and from Mali to Lebanon. Preventing water-related conflicts can save lives and is good for the economy. The Water, Peace and Security (WPS) partnership and the Geneva Water Hub show how water-related conflict prevention looks in practice, and how to measure the success of such programs. Clarity about programming and measuring impact are needed to unlock more investment in conflict prevention and to do so efficiently and effectively.