Natural capital refers to those stocks of assets provided for free by nature which, directly or indirectly, deliver well-being for humans. These include freshwater, fertile soils, clean air and living things. Natural capital stocks deliver flows of services, often called ecosystem services, which (often in combination with flows from other capital including human labour, ingenuity and manufactured goods) produce the benefits upon which humans depend for economic well-being and their very existence. Economic activity depends on natural capital while also affecting the stock of those assets. This relationship between the environment, the economy and human well-being has caught the attention of governments at both global and national levels. But how should governments incorporate the notion of natural capital into policy- and decision-making? We set out to define the notion of natural capital and how it can be brought into the economic analyses which underpin the majority of policy decision-making systems. We consider the means by which changes can be best directed to reflect the underlying science of the environment, the incentives of the economy and the preferences of society.