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 South Dakota, tortious interference with a contract or business expectancy is recognized as a legitimate legal claim. This type of civil claim arises when a third party, who is not part of an existing contract, intentionally interferes with that contract or a prospective business relationship that is likely to occur, causing harm to one of the parties involved. The third party's actions must typically go beyond mere competition and involve some form of improper conduct, such as deceit, coercion, or direct persuasion to breach the contract. South Dakota law requires the plaintiff to prove that the interference was intentional and that it resulted in damages. While competitive behavior is generally permissible, it crosses the line into tortious interference when it involves wrongful means or is intended to harm the business relationship. The specifics of what constitutes wrongful means can vary, and an attorney can provide guidance on the current standards and how they might apply to a particular case.