This timely Companion examines how peace and sustainable development are closely linked, and why progress on the United Nations' Sustainable Development Goals (SDGs) cannot be achieved without addressing armed conflict and weak institutions. Leading experts argue that, while the SDGs aim to improve living standards worldwide, violent conflict and instability continue to undermine gains in poverty reduction, gender equality, health, and climate action. Presenting interdisciplinary evidence, the chapters scrutinize peace as an enabling condition shaped by governance and trust, while confronting the methodological and practical challenges of working in conflict-affected settings. Systematically exploring each SDG, they examine why peace is frequently sidelined in development planning and how improved data, institutions, and cooperation could help close this gap. The Companion argues that lasting development depends on treating peace as foundational, rather than a secondary goal. Scholars and students of development studies, peace and conflict studies, political science, and international relations will greatly benefit from this Companion 's extensive analysis of peace as a pre-requisite for global progress. Policymakers and professionals in international development and humanitarian affairs will also find its innovative recommendations immensely useful.