For major physical diseases, it is widely accepted that members of the public will benefit by knowing what actions they can take for prevention, early intervention, and treatment. However, this type of public knowledge about mental disorders ("mental health literacy") has received much less attention. There is evidence from surveys in several countries for deficiencies in (a) the public's knowledge of how to prevent mental disorders, (b) recognition of when a disorder is developing, (c) knowledge of help-seeking options and treatments available, (d) knowledge of effective self-help strategies for milder problems, and (e) first aid skills to support others affected by mental health problems. Nevertheless, there is evidence that a range of interventions can improve mental health literacy, including whole-of-community campaigns, interventions in educational settings, Mental Health First Aid training, and information websites. There is also evidence for historical improvements in mental health literacy in some countries. Increasing the community's mental health literacy needs to be a focus for national policy and population monitoring so that the whole community is empowered to take action for better mental health. (Contains 3 tables and 2 figures.)