Undue influence in English law is a field of contract law and property law whereby a transaction may be set aside if it was procured by the influence exerted by one person on another, such that the transaction cannot "fairly be treated the expression of [that person's] free will".

Royal Bank of Scotland plc v Etridge [2001] UKHL 44 is a leading case relevant for English land law and English contract law on the circumstances under which actual and presumed undue influence can be argued to vitiate consent to a contract.