This report is the result of a six-month study conducted in France and abroad. It provides an overview of the current landscape regarding data collected on a regular or ad hoc basis that is relevant to mental health surveillance. It is based on the information needs identified by the stakeholders and decision-makers interviewed—ranging from healthcare providers, administrators, and researchers to service users—in the field of mental health. It is informed by scientific and ethical debates in the fields of public health and mental health regarding the best ways to understand mental health and its determinants, and to define and monitor it. It draws on the recommendations of French and international institutes and organizations.