Cavendish Square Holding BV v Talal El Makdessi [2015] UKSC 67, together with its companion case ParkingEye Ltd v Beavis, are English contract law cases concerning the validity of penalty clauses and the application of the Unfair Terms in Consumer Contracts Directive. The UK Supreme Court ruled on both cases together on 4 November 2015, updating the established legal rule on penalty clauses and replacing the test of whether or not a disputed clause is "a genuine pre-estimate of loss" with a test asking whether it imposed a proportionate detriment in relation to any "legitimate interest" of the innocent party.

English contract law is the body of law that regulates legally binding agreements in England and Wales. With its roots in the lex mercatoria and the activism of the judiciary during the Industrial Revolution, it shares a heritage with countries across the Commonwealth, from membership in the European Union, continuing membership in Unidroit, and to a lesser extent the United States. Any agreement that is enforceable in court is a contract. A contract is a voluntary obligation, contrasting to the duty to not violate others rights in tort or unjust enrichment. English law places a high value on ensuring people have truly consented to the deals that bind them in court, so long as they comply with statutory and human rights.