We have built particle accelerators to understand the forces that make up our physical world. Yet, we do not understand the principles underlying our strongly connected, techno-socio-economic systems. We have enabled ubiquitous Internet connectivity and instant, global information access. Yet we do not understand how it impacts our behavior and the evolution of society. To fill the knowledge gaps and keep up with the fast pace at which our world is changing, a Knowledge Accelerator must urgently be created. For this, the FuturICT flagship project will promote an interdisciplinary integration of natural, social, and engineering sciences with novel paradigms of information technology. This will produce the synergy effects required to address many of our 21st century challenges. After the age of physical, biological and technological innovations, FuturICT will lead Europe into the next era – a wave of information-driven social and socio-inspired innovations. Globalisation and technological change have made our world a different place. This has created or intensified a number of serious problems, such as global financial and economic crises, political instabilities and revolutions, the quick spreading of diseases, disruptions of international supply chains, organised crime, international conflict and world-wide terrorism, and increased cyber-risks as well. Although the creation of more and more interconnected systems and the pace of innovation in the area of information and communication technologies (ICT) have contributed to the above problems, future ICT can also be key to the solution. It can create unprecedented benefits for our economy and society, based on a whole range of new methods and innovations. For this, ICT must acquire the ability to flexibly adapt to the needs of society. In this way, it can become a stabilising factor fostering transparency, trust, respect for individual rights, and opportunities for participation in social, economic, and political processes. This requires us to establish a new science of multi-level complex, global systems and a co-evolution of ICT with society, by bringing the best knowledge of experts on information and communication systems, complex systems and the social sciences together. The vision of the FuturICT flagship project is to develop the capacity to explore and manage our future, based on a fundamental understanding of the institutional and interaction-based principles that make connected systems work well. The methods and ‘Big Data’ needed for such a scientific endeavour are now becoming available: it is, therefore, time to make a ‘Big Science’ effort to couple methods and data with theories and models, like in the Human Genome Project. This endeavour should be open, because we need to prevent private monopolies of socio-economic data, and it should be federated, because joint interdisciplinary efforts are the only way to tackle humanity’s global challenges and ensure leadership in socio-inspired ICT innovations. The investments into the FuturICT project can benefit citizens and society in many ways: by promoting collective awareness of the impacts of our decisions and actions, by mitigating global problems and systemic risks, and by creating new possibilities to participate in social, economic and political affairs. In particular, FuturICT will create the basis for new spin-offs, business opportunities and jobs.