In January 2018, UNESCO, together with UNAIDS, UNFPA, UNICEF, UN Women, and the WHO, completed the substantial technical and political process of updating the International Technical Guidance on Sexuality Education, thereby unifying a UN position on rationale, evidence, and guidance on designing and delivering comprehensive sexuality education (CSE). The revised Guidance builds on the original Guidance, with improvements and updates based on new evidence and good practice documented from across the globe. User-surveys and structured consultations with representatives from a wide range of fields and interest-groups informed and guided the revision process. The revised Guidance presents one, commonly agreed definition of CSE; enhances and expands its key concepts, topics and learning objectives; places a strengthened focus on gender and human rights; provides guidance on building support and planning the implementation of CSE programmes; and reflects the contribution of CSE to the realization of multiple Sustainable Development Goals (SDGs). With its unified voice, progressive position, and attention to key implementation challenges, the revised Guidance is a responsive, timely, and critically needed tool to advance towards a tipping point for the large-scale application of quality CSE.