Williams v Roffey Bros & Nicholls (Contractors) Ltd [1989] EWCA Civ 5 is a leading English contract law case. It decided that in varying a contract, a promise to perform a pre-existing contractual obligation will constitute good consideration so long as a benefit is conferred upon the 'promiseor'. This was a departure from the previously established principle that promises to perform pre-existing contractual obligations could not be good consideration.