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 Washington State, tortious interference with a contract or business expectancy is recognized as a legal cause of action. This occurs when a third party, who is not part of an existing contract, intentionally interferes with the contractual relations or prospective business relations of others, causing damage. The elements of this tort typically include the existence of a valid contractual relationship or business expectancy, the third party's knowledge of this relationship, intentional interference inducing or causing a breach or termination of the relationship or expectancy, and resultant damage to the party whose relationship or expectancy has been disrupted. Washington courts may require that the interference be improper or without justification. The state acknowledges the balance between protecting contractual and business relationships and allowing for legitimate competition, meaning not all competitive acts that interfere with a contract will lead to liability. It is important for parties considering a claim of tortious interference in Washington to consult with an attorney to understand the nuances of state law and to assess the validity of their claim.