HLPI, or High-Impact, Low-Probability events, are characterized by a slight likelihood of occurrence but the potential for severe, often catastrophic consequences.

These events challenge conventional risk management frameworks because their infrequent nature makes precise probability quantification difficult and can lead to underestimation of potential damage. Examples include major infrastructure failures, global pandemics, or extreme climatic shifts.

The primary difficulty lies in balancing the cost of proactive resilience measures against the low perceived chance, or 'Black Swan' type, of the events, which often leads to risk neglect or insufficient investment in mitigation measures.

Effective HLPI risk management demands shifting the focus from statistical prediction toward building system robustness and utilizing comprehensive scenario planning.