Interpleader is a civil procedure device that allows a plaintiff or a defendant to initiate a lawsuit in order to compel two or more other parties to litigate a dispute. An interpleader action originates when the plaintiff holds property on behalf of another, but does not know to whom the property should be transferred. It is often used to resolve disputes arising under insurance contracts, such as when a plaintiff with a personal injury claim has a dispute with medical providers over the payment out of a settlement for medical services provided to treat the plaintiff's injuries.

In an interpleader action, the party initiating the litigation, normally the plaintiff, is termed the stakeholder. The money or other property in controversy is called the res (a Latin word meaning object or thing). All defendants having a possible interest in the subject matter of the case are called claimants. In some jurisdictions, the plaintiff is referred to as the plaintiff-in-interpleader and each claimant a claimant-in-interpleader.

An interpleader proceeding has two stages. The first stage determines if the stakeholder is entitled to an interpleader and if he should be discharged from liability. The second stage is like an action at law to determine which of the claimants is entitled to the res.

Suppose a person dies with a valid life insurance policy in effect. The insurance company is ready, willing, and able to pay the policy proceeds in specified percentages to named beneficiaries as last directed by the policyholder, but becomes aware of a dispute among them and/or third parties as to who are the proper beneficiaries or the proper distribution of proceeds among the beneficiaries. Such a dispute commonly arises from interpersonal friction among the policyholder's survivors. One specific situation commonly seen in the reported cases is where the policyholder was allegedly murdered by a beneficiary (which would disqualify that beneficiary from receiving any proceeds).

To resolve such a dispute, the insurance company can file an interpleader action. The insurance company is the stakeholder, the claimants are the persons who might be beneficiaries under the policy, and the cash value of the policy benefit is the res. Under the proceeding as originally developed, the stakeholder would deposit the res with the court, and then the defendants would have their claims adjudicated by the court. Statutory modifications to the procedure, which vary by jurisdiction, sometimes allow the stakeholder to retain the res pending final disposition of the case. Typically, once the stakeholder deposits the res into the court (for example, the face value of the insurance policy), the stakeholder is released from the action and the claimants proceed against each other to determine which of them is legally entitled to the res. A disinterested stakeholder is entitled to costs including attorney's fees. Except for the denominations of the parties, the action proceeds for the most part as other civil lawsuits in the same jurisdiction.

In some jurisdictions, the res will earn interest at the legal rate until disbursed. The successful claimant is entitled to the interest as well as the principal.

Interpleader had its origins as a civil procedure at common law, which was later adopted and expanded by the Court of Chancery in its equitable jurisprudence. The common law procedure became obsolete over time and fell into disuse, but it remained active in the courts of equity.

It originally applied to bailees subject to multiple actions of detinue, and privity was required either between the parties or in detinue, in order for the defendant to be able to sue for garnishment.