Lancet, Published:February 21, 2019DOI:https://doi.org/10.1016/S0140-6736(19)30424-6. This article announce the establishment of Countdown Global Mental Health, an independent, multistakeholder monitoring and accountability collaboration for mental health, within an initial timeframe of the UN Sustainable Development Goals (SDGs). The scope of the Countdown will be global since mental health is an issue relevant to all countries. The unit of analysis will be countries or states or provinces within large federated countries. Given the huge disparities between and within countries, we expect the Countdown to be a strong instrument for accountability to decrease population-level disparities for mental health.