Doyne Farmer is an American physicist and complexity scientist known for his work in the fields of chaos theory, complex systems, and financial markets. He is a professor at the Santa Fe Institute, where he studies how complex systems behave and evolve over time. Farmer has contributed significantly to understanding how small changes can lead to unpredictable outcomes in various systems. In addition to his academic work, Farmer is also an entrepreneur. He co-founded Predictive Analytics and has been involved in developing models that apply scientific principles to economic forecasting. His research has implications for fields ranging from economics to ecology.