In collaboration with the APPG on Mental Health, this report considers what the UK is currently doing to improve mental health globally and whether UK expertise and resources could be more effectively used to meet this challenge. The simple message of this report is that progress in development will not be made without improvements in mental health. Mental illnesses cause more disability than any other health condition; bring enormous pain and suffering to individuals and their families and communities; and can lead to early death, human rights abuses and damage to the economy. Improving mental health is therefore a vital part of a successful development programme.