A Union is a single entity which is a collection of two or more entities.

Other references are:

• A mathematical concept: see union (set theory)
• A political entity of states: see personal union
• The United States of America, particularly in reference to actions during the American Civil War (see Union (American Civil War))
• The European Union
• The African Union
• A type of legal entity: see union (commerce)
• A trade union (also known as a labor union or labour union) is a workers' organization designed to assist in employment negotiation.
• A datatype; see union (computer science)
• Civil union - a commitment ceremony similar to but legally distinct from marriage
• The successful fusion of a fractured bone.
• Union College - a college in Schenectady, New York and other places.
• Union of India - was the official name of India before it became a republic.
• Union Theological College - a college in Northern Ireland
• The United States Republican Party was also known as the Union Party during the 1864 election cycle.

• A common place name (especially in the United States of America):
  • Union, Alabama
  • Union, Connecticut
  • Union, Illinois
  • Union, Iowa
  • Union, Kentucky
  • Union, Maine
  • Union, Mississippi
  • Union, Missouri
  • Union, Nebraska
  • Union, New Jersey
  • Union, New York
  • Union, Ohio
  • Union, Oregon
  • Union, South Carolina
  • Union, West Virginia
  • Union, Wisconsin
  • Union, Saint Vincent
  • Union, Grenadines (in the Caribbean)
  • Union City, California
  • Union City, Georgia
  • Union City, Indiana
  • Union City, Michigan
  • Union City, New Jersey
  • Union City, Ohio
  • Union City, Pennsylvania
  • Union City, Tennessee
  • Union County, Arkansas
  • Union County, Georgia
  • Union County, Illinois
  • Union County, Indiana
  • Union County, Iowa
  • Union County, Kentucky
  • Union County, Mississippi
  • Union County, New Jersey
  • Union County, New Mexico
  • Union County, North Carolina
  • Union County, Ohio
  • Union County, Oregon
  • Union County, Pennsylvania
  • Union County, South Carolina
  • Union County, South Dakota
  • Union County, Tennessee
  • Union Township, Michigan
  • Union Township, New Jersey
  • Union Township, Pennsylvania
• Similar placenames include:
  • Mount Union, Iowa
  • Uniontown
  • Unionville
  • Union Beach, New Jersey
  • Union Grove, Alabama
  • Union Hill, Illinois
  • Union Park, Florida
  • Union Parish, Louisiana
  • Union Springs, Alabama
  • Union Springs, New York
  • West Union, Iowa