Service of process is the term given to legal notice of a court or administrative body's exercise of its jurisdiction over individuals who are the subject of proceedings or actions brought before such court, body or other tribunal. In most Anglo-American legal systems the service of process is effectuated by a process server, usually an adult who does not have an interest in the outcome of the litigation. Each jurisdiction has rules regarding the service of process, in some cases the law may require the summons to be served upon the person personally, or upon the person or someone of suitable age and discretion at the persons abode or place of business or employ.

In some cases service of process may be effected through the mail as in some small claims procedures. Often the court or procedural rules allow for the service of process by court order or by publication when an individual cannot be located in a particular jurisdiction. In some jurisdictions process is completed by sheriffs or bailiffs. In the French legal system, the task is performed by a huissier. There may be licensing requirements as in New York City. In some places the parties themselves may effectuate service. Proper service of process results in "personal jurisdiction" of the court over the person served. If they ignore further pleadings or fail to participate in the proceedings brought against them the court or administrative body may find them in default and award relief to the claimant, petitioner or plaintiff.

In ancient times the service of a summons was considered a royal act that had serious consequences. It was a summons to come to the King's Court and to respond to the demand of a loyal subject. In ancient Persia, failure to respond to the King's summons meant a sentence of death. Today the penalties for ignoring a summons are usually money judgments that must be subsequently enforced.