An Act of God is a natural force outside of human control (such as an earthquake, tsunami, or hurricane), and may relieve a party or parties to a contract or agreement from having to perform their obligations. Such Acts of God are often addressed in a force majeure clause, which typically appears near the end of the contract or agreement. A force majeure clause may also excuse a party's performance of its obligations for other reasons beyond its control, such as unavailability of products, riots, civil unrest, pandemics, and terrorism.

In Illinois, an 'Act of God' refers to unforeseen natural events that are beyond human control and cannot be anticipated or prevented, such as severe weather events, earthquakes, or pandemics. These events may excuse parties from fulfilling their contractual obligations if such obligations become impossible to perform due to these extraordinary circumstances. Force majeure clauses are contractual provisions that define the scope of unforeseeable events that can relieve parties from their contractual duties. Illinois courts typically enforce these clauses according to their specific terms, which means that the actual language of the force majeure clause is critical in determining whether an event qualifies as an Act of God and whether it excuses performance. If a force majeure clause explicitly includes events like pandemics or civil unrest, parties may be excused from performance when such events occur. However, without a force majeure clause, parties may still invoke the common law doctrine of impossibility or impracticability of performance, but this is a more challenging argument to make and requires a showing that the unforeseen event has rendered the performance of the contract truly impossible or impracticable.