A condominium (or condo for short) is a building structure divided into several units that are each separately owned, surrounded by common areas that are jointly owned.

Residential condominiums are frequently constructed as apartment buildings, but there are also "detached condominiums", which look like single-family homes, but in which the yards (gardens), corridors, building exteriors, and streets as well as any recreational facilities (like a pool or pools, bowling alley, tennis courts, golf course, etc.), are jointly owned and maintained by a community association.

Unlike apartments which are leased by their tenants, condominium units are owned outright. Additionally, the owners of the individual units also collectively own the common areas of the property, such as corridors/hallways, walkways, laundry rooms, etcetera, as well as common utilities and amenities, such as the HVAC system, elevators, and so on. Many shopping malls are industrial condominiums in which the individual retail and office spaces are owned by the businesses that occupy them while the common areas of the mall are collectively owned by all the business entities that own the individual spaces.

The common areas, amenities, and utilities are managed collectively by the owners through their association, such as a homeowner association.

Scholars have traced the earliest known use of the condominium form of tenure to a document from first-century Babylon. The word condominium originated in Latin.

Condominium is an invented Latin word formed by adding the prefix con- ‘together’ to the word dominium ‘dominion, ownership’. Its meaning is therefore ‘joint dominion’ or ‘co-ownership’.

Condominia (the Latin plural of condominium) originally referred to territories over which two or more sovereign powers shared joint sovereignty. This technique was frequently used to settle border disputes when multiple claimants could not agree on how to partition the disputed territory. For example, from 1818 to 1846, Oregon Country was a condominium over which both the United States and Great Britain shared joint sovereignty until the Oregon Treaty resolved the issue by splitting the territory along the 49th parallel and each country gaining sole sovereignty of one side.