Tortious interference with contract—also known as intentional interference with contractual relations or business expectancy—is a civil claim or cause of action based on interference with a contract or a prospective contract that is about to be completed—by a person or entity who is not a party to the contract (third party).

A claim for tortious interference is based on the idea that the third party encouraged or induced one of the parties to the contract to breach the contract, causing damages to the nonbreaching party, who may sue the third party to recover those damages or losses. In some states there is a requirement that the interference be done maliciously or without justification.

Laws regarding claims for tortious interference with contract vary from state to state. Some states have broadened the protections against interference beyond situations where there is an existing contract and recognize claims for interference with prospective economic advantage or business relations.

But whether there is an existing contract or not, some instances of interference will not create legal liability and will be recognized as legitimate competitive activity, for example.

In New York, tortious interference with contract is recognized as a valid legal claim. To establish a claim for tortious interference with a contract, a plaintiff must prove the existence of a valid contract between the plaintiff and a third party, the defendant's knowledge of that contract, the defendant's intentional procurement of the third-party's breach of the contract without justification, actual breach of the contract, and damages resulting therefrom. New York courts also recognize a cause of action for tortious interference with prospective economic advantage, which protects business relationships not yet formalized into a contract. However, this claim requires the plaintiff to demonstrate that the defendant's interference was intentional and malicious, meaning it was done with the sole purpose of harming the plaintiff. Competitive behavior that is part of fair play in business is generally not actionable under this doctrine. It is important for parties who believe they have been harmed by such interference to consult with an attorney to understand the nuances of these claims and to assess the strength of their case under New York law.