Personal jurisdiction, jurisdiction of (or over) the person, or jurisdiction in personam is the power of a court to require a party (usually the defendant) or a witness to come before the court. The court must have personal jurisdiction to enforce its judgments or orders against a party.

Personal jurisdiction is distinguished from subject-matter jurisdiction and jurisdiction in rem.

In a civil case, personal jurisdiction over a defendant is obtained by service of a summons. Personal jurisdiction over a witness is obtained by service of a subpoena. Service can be accomplished by personal delivery of the summons or subpoena to the person or an authorized agent of the person. Service may also be made by substituted means; for example, in many jurisdictions, service of a summons can be made on a person of suitable age and discretion at the residence or place of business of the defendant. Jurisdiction over corporations can often be obtained through a government body authorized to receive such process. In some jurisdictions the Clerk of the Court may be authorized to accept legal process for persons who cannot otherwise be found.

Traditionally, in civil proceedings in the United States, the defendant was required to be physically present, at the time he or she was served with a summons, in the state where the court sits. Over the years, the reach of personal jurisdiction was expanded by judicial interpretations and legislative enactments. For example, states in the United States have statutes that govern obtaining personal jurisdiction over out of state motorists who are involved in accidents within a state. In addition, the states have enacted provisions for "long arm jurisdiction," by which the courts can exercise jurisdiction over a business entity or individual located outside the state, if (for example) the out-of-state entity or individual regularly does business in the state or transacted business with the plaintiff within the state.

The Supreme Court of the United States has held that constitutional requirements of due process limit the state courts' exercise of personal jurisdiction over nonresidents. In general, to be subject to personal jurisdiction, a defendant that was not personally served with process within the state must have a sufficient level of personal or business contacts with the state in which the court sits that the defendant could reasonbly expect to be sued there. These contacts are sometimes referred to by the term of art "minimum contacts". Generally speaking, a party is subject to personal jurisdiction in a state if the party has purposely availed itself of the resources of protection of the state.

Normally, the personal jurisdiction of a United States District Court is concurrent with the personal jurisdiction of the courts of the state in which it sits. In some circumstances, however, statutes and rules of court allow the federal District Courts to exercise nationwide personal jurisdiction or to exercise personal jurisdiction over foreign persons or entities based on their contacts with the United States as a whole.

Personal jurisdiction in the United States is divided into two categories. A court may exercise jurisdiction if it finds either general or specific jurisdiction over a party. General jurisdiction exists when a party has extensive dealings with the region of territory administered by the court. Specific jurisdiction is present when a party performed some activity in the territory without which the present action before the court could not have been brought.