This paper introduces, describes and analyses the emerging concept of Global Mental Health (GMH). The birth of GMH can be traced to London, 2007, with the publication of a series of high-profile papers in The Lancet. Since then, GMH has developed into a movement with proponents, adherents, opponents, an ideology and core activities. The stated aims of the Movement for GMH are ‘to improve services for people living with mental health problems and psychosocial disabilities worldwide, especially in low- and middle-income countries where effective services are often scarce’. GMH could be considered an attempt to right a historic wrong. During the colonial and post-colonial eras, the mental health of subject populations was accorded a very low priority. This was fuelled by scientific racism, which alleged that mental illness was uncommon in places such as Africa. As developing nations have made the epidemiological transition, the burden of mental illness has proportionately increased, with research suggesting a massive ‘treatment gap’ between those in need and those actually receiving formal mental health care. As such, much GMH research and action has been devoted to: (i) the identification and scale-up of cost-effective evidence-supported interventions that could be made more widely available; (ii) task-shifting of such intervention delivery to mental-health trained non-specialist Lay Health Workers. GMH has come under sustained critique. Critics suggest that GMH is colonial medicine come full circle, involving the top-down imposition of Western psychiatric models and solutions by Western-educated elites. These critiques suggest that GMH ignores the various indigenous modalities of healing present in non-Western cultures, which may be psychologically adaptive and curative. Relatedly, critics argue that GMH could be an unwitting Trojan horse for the mass medicalisation of people in developing countries, paving the way for exploitation by Big Pharma, while ignoring social determinants of health.