Leaving no one behind (LNOB) is the central, transformative promise of the 2030 Agenda and its SDGs. This operational guide has been developed by the UNSDG to strengthen the UNDS’ support of implementation of the 2030 Agenda’s commitment to LNOB at the national level. The guide provides a step-by-step approach to operationalizing Member States’ pledge to leave no one behind and reach the furthest behind first. It builds on the CEB-endorsed Equality and Non-Discrimination at the Heart of Sustainable Development: a Shared UN Framework for Action, UNSDG programming principles including the Human Rights-Based Approach to Development, and UNSDG guidance and tools to support SDG achievement (eg. MAPS). Annexes contain additional resources relevant to the steps outlined in the guide.