Multiplicity of actions describes a situation where substantially the same dispute is pursued through two or more sets of legal proceedings, often in different courts or between overlapping parties. It commonly arises where parallel claims, duplicative proceedings or fragmented litigation risk inconsistent judgments, wasted costs and inefficient use of court resources.In the UK and Ireland, “multiplicity of actions” is generally a descriptive expression rather than a defined statutory term. It appears frequently in case law and procedural argument, particularly in applications for case management stays, striking out, abuse of process, forum non conveniens and anti‑suit injunctions.Courts in England & Wales, Scotland, Northern Ireland and Ireland share a common objective of avoiding multiplicity of actions. Judges may respond by: staying one set of proceedings; ordering consolidation or transfer; striking out as an abuse of process; or giving directions to coordinate related cases.In cross‑border and commercial litigation, addressing multiplicity of actions is crucial to risk management, controlling litigation costs and reducing the danger of conflicting decisions, especially where parallel proceedings are on foot in another UK jurisdiction, Ireland, or overseas courts.