In organizations

• Civil union, a commitment ceremony similar to marriage
• Credit union, a co-operative financial institution
• Trade union, a workers' organization (called a labor union in American English)
• Poor Law union, a group of parishes providing relief in the United Kingdom
• Rugby union, a type of rugby football
• Students' union, an organization on a university campus that brings together students

In politics

• African Union, an inter-governmental organization in Africa
• European Union, an inter-governmental organization in Europe
• Government of India, known officially as the Union Government
• Personal union, a group of separate, independent states that share the same monarch
• Political union, a type of state composed of smaller states
• Union (American Civil War), those states of north of the United States during the American Civil War
• The Union (political coalition) (l'Unione), an twenty-first century Italian political coalition
• Unionist Party (Canada), known when in power as the Union Government
• United States Republican Party, known as the Union Party during the 1864 election

In science and mathematics

• Union (set theory), a mathematical concept
• Union (computer science), a data structure in some programming languages
• Union (SQL), an SQL command

In sports and entertainment

• A group of professional wrestlers in opposition to Vince McMahon in the World Wrestling Federation
• The supporters' club of the A-League football side Melbourne Victory
• Union (album), a 1991 album by the musical group Yes
• Union (band), an American heavy metal band

In education

• Union College (Kentucky), a college in Kentucky
• Union College, a college for which the principal campus sits in Schenectady, New York
• Union Institute & University, a non-traditional educational institution
• Union Theological College, a college in Northern Ireland
• Union Theological Seminary in the City of New York, an ecumenical Christian seminary in New York City, New York
• Union Theological Seminary & Presbyterian School of Christian Education, a Christian seminary in Richmond, Virginia
• Union University, a Baptist college in Tennessee

In transportation

• Union Railroad, any of several railroad companies

In tradesmanship

• Union (electrical), a term sometimes used for a butt connector used to splice wires
• Union (hardware), a term sometimes used for a standoff that serves as an elongated nut
• Union (plumbing), a pipe fitting

In geography

• Union Station, any of several depots at which two or more railway, subway, or bus lines merge
• 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
• 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
• 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