An injunction is an equitable judicial remedy issued at the court's discretion. It usually takes the form of an order preventing or restraining a person from performing an act. The order may also take a mandatory form by compelling someone to do something. It may be sought as a final remedy or at a preliminary stage before trial (the interlocutory injunction). The injunction is designed to provide more effective and appropriate relief than an ordinary common-law award of damages. In many circumstances applicants prefer to have an act prevented or performed rather than to receive compensation after the fact.

There are two basic types of injunctions: mandatory and prohibitive. Mandatory injunctions require a person to perform an act, usually within the context of remedying past wrongs committed by that person. Prohibitive injunctions prevent a person from performing an act, and are designed to prevent that person from committing wrongs to the detriment of others. They can be permanent or temporary and are generally favoured by courts as opposed to mandatory injunctions.

Injunctions are best suited to situations where an award of damages would be an inadquate way of compensating an aggrieved person. The basic test used in determining whether to grant an injunction is as follows: has the plaintiff established a case worthy for trial; will damages be an adequate remedy; and could the plaintiff adequately compensate the defendant for loss suffered by the defendant if, at the end of the day, the plaintiff were wrong?

An adjunct to the above test is the "balance of convenience (or inconvenience)" test. A court must compare whether not granting the plaintiff an immediate remedy will so impair the plaintiff's rights that, by the time of final judgement, the plaintiff will have suffered irreparable harm less than or greater than the extent the defendant will be harmed if the injunction is granted.

A famous and common type of injunction is known as a Mareva injunction and is named after an English court decision. A Mareva injunction can be given to a plaintiff and has the effect of preventing a defendant from disposing of assets prior to trial, thereby protecting the plaintiff's potential claim for monetary damages.

Failure to abide by the terms of an injunction can expose a Defendant to a finding of civil or criminal contempt of court, where fines or imprisonment can be imposed.