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 Massachusetts, tortious interference with contract, also known as intentional interference with contractual relations, is recognized as a civil cause of action. To establish a claim for tortious interference, a plaintiff must prove that there was a valid contract or a business expectancy; the defendant was aware of this contract or expectancy; the defendant intentionally interfered with it, inducing or causing a breach or termination of the relationship or expectancy; and the plaintiff suffered damages as a result. The interference must also be improper in motive or means. Massachusetts courts have recognized that not all interferences are actionable, particularly when they involve legitimate business competition. The interference must be done with malice or without justification to be considered tortious. The state also recognizes claims for interference with prospective economic advantage or business relations, which protect a plaintiff's potential business opportunities even in the absence of an existing contract.