This chapter introduces the concepts of natural capital and ecosystem services, highlights their application in sustainable finance and discusses the challenges their use raises. The terms present a framework for thinking through environmental, social and economic problems associated with sustainable natural resource management and the distribution of benefits. Their quantification in monetary terms enables policymakers to assess the social costs and benefits of investments in environmental conservation, sustainable development and resource use at differing spatial and temporal scales. The approach by The Economics of Ecosystems and Biodiversity (TEEB) study, to reveal, demonstrate and capture ecosystem service values helps bring the concepts out of academia and into policymaking and, recently, into business so it can measure its impacts and dependencies on nature. The concepts have also been integral to developing consistent, comprehensive, standardised accounting frameworks to augment traditional measures of human wellbeing, such as gross domestic product (GDP), thus making the contributions of nature to the human economy more transparent. The concepts have their critics. Non-linearity and complexity in ecosystem service provision, as well as economic values, notably monetary value can confound valuation techniques. These obscure the reality that nature has intrinsic value, regardless of human systems of valuation.