This article introduces a Special Issue on the Protection of Civilians (PoC) efforts in United Nations (UN) peacekeeping operations. The UN Security Council adopted Resolution 1265 in February 1999, laying the basis for PoC becoming a fundamental part of UN peacekeeping. On the 25th anniversary of this resolution, it?s time to reflect on the various advances, achievements and challenges facing the UN?s PoC agenda. This introduction to the Special Issue outlines the UN?s three-tiered PoC approach: dialogue and engagement, physical protection, and creating a protective environment. Building on this foundation, the Special Issue explores diverse topics, including pre-deployment training, unarmed peacekeeping, host-state consent, military and police roles in protection, the use of force by troops, civilian protection sites in South Sudan, and the unintended effects of peacekeeping missions. Each article contributes insights across the three PoC tiers bringing together cutting edge insights from leading academics and practitioners in the field.