IUCN World Heritage Outlook 3 builds on three cycles of Conservation Outlook Assessments undertaken since 2014. It presents the main results for 2020, but also some longer-term trends based on a comparison of three data sets now available. As such, it can ser ve as an indicator of the effectiveness of protected and conserved areas at a time when the international community seeks to measure progress towards global biodiversity targets and defines the Post-2020 Global Biodiversity Framework. Focusing on the natural values for which sites are inscribed, threats to these values, and the effectiveness of actions to protect them, the IUCN World Heritage Outlook assesses the conservation prospects of all natural World Heritage sites. These sites are globally recognised as the most significant natural areas on Earth and their conservation must meet the high standards of the World Heritage Convention. Our ability to conserve these sites is thus a litmus test for the broader success of conservation worldwide. Securing a positive outlook for these sites is a priority, as expressed in the Promise of Sydney carried by IUCN’s World Parks Congress in 2014.