Space Security Index 2019 is the 16th annual report on developments related to safety, sustainability, and security in outer space. It is part of the broader Space Security Index (SSI) project, which aims to improve transparency on space activities and provide a common, comprehensive, objective knowledge base to support the development of dialogue and policies that contribute to the governance of outer space as a shared global commons. Inside this report, you will find contextual information and annual updates on 17 indicators of space security, organized under four broad themes. This arrangement is intended to reflect the increasing interdependence, mutual vulnerabilities, and synergies of outer space activities.