Our future is uncertain, shaped by a multitude of powerful, complex and interconnected forces, eventually altered by improbable, unpredictable and highly disruptive events. Seen over a time horizon of say 10-20 years, some of the big trends we see unfolding before us are in fact quite slow-moving. These are megatrends – large-scale social, economic, political, environmental or technological changes that are slow to form but which, once they have taken root, exercise a profound and lasting influence on many if not most human activities, processes and perceptions. Such relative stability in the trajectory of major forces of change allows some elements of a likely medium-to-long term future to be envisioned, at least with some degree of confidence. The OECD STI Outlook 2016 covers those megatrends that are expected to have strong impact on science, technology and innovation systems over the next 10-15 years. The megatrends covered are clustered into eight thematic areas as follows: Demography, Natural resources and energy, Climate change and environment, Globalisation, Role of government, Economy, jobs and productivity, Society, and Health, inequality and well-being.