Many of the systemic risks that we will need to address in the 21st century depend crucially on the often unanticipated consequences of interactions within and between different types of systems. The emerging, interdisciplinary field of complex systems provides a shared language as well as mathematical and computational models that can help us understand the challenges we face in this increasingly interconnected world. In this seminar series, leading researchers will explore the implications of a complex systems approach for systemic risks in ecosystems, financial systems, urban systems, and human societies.