Foakes v Beer [1884] UKHL 1 is an English contract law case, which applied the controversial pre-existing duty rule in the context of part payments of debts.

It established the rule that prevents parties from discharging an obligation by part performance, affirming Pinnel's Case (1602) 5 Co Rep 117a.

The appellant, Dr John Weston Foakes, owed the respondent, Julia Beer, a sum of £2,090 19s after a court judgment.

However, the promise to pay a debt was deemed not to be sufficient consideration as there was no additional benefit moving from Foakes to Beer that was not already owed to her.

I assent to the judgment proposed, though it is not that which I had originally thought proper.Barely more than a restatement of the ancient rule in Pinnel's case, Foakes v Beer was effectively treated as per incuriam by Lord Denning in Central London Property Trust Ltd v High Trees House Ltd, on the basis that in 1884 the court in Foakes had failed to pay cognisance to the 1877 case of Hughes v Metropolitan Railway Co, which had introduced the concept of promissory estoppel.