This article will discuss the concept of the black swan, the extreme impact of rare and unpredictable events, as applied to chemical process risk assessment. Lessons learned from black swan events of the past and the applicability of these lessons to the design and operations of existing and new chemical processing facilities will be discussed. The limitations of layer of protection analysis (LOPA) and other risk analysis tools in predicting black swan events will be examined. The discussion on the limitations of risk analysis will include examples of hazards scenarios where risk analysis tools such as LOPA may not be appropriate. (c) 2012 American Institute of Chemical Engineers Process Saf Prog, 2012.