"Home nation" (common noun) redirects here; home nation is also used to refer to the host country of multi-sport events (eg. the Olympics), or other international sports championships.
Home Nations (often written as the common noun home nations) is a term used to refer to the four constituent countries of the United Kingdom — England, Scotland, Wales and Northern Ireland — collectively but as separate entities, distinct from the United Kingdom as a state.

Sporting events
The term is often used when referring to sporting events in which each Home Nation competes separately, such as the now defunct British Home Championship in football. When the term came into use is not known, but it is fair to assume that before the partition of Ireland into the still-British Northern Ireland and the independent Irish Free State (now the Republic of Ireland) in 1922, all of Ireland was considered to be a Home Nation (as all of it was part of the UK). This traditional usage is still seen today in the context of sports such as rugby union; the Ireland national rugby union team represents both Northern Ireland and the Republic of Ireland. It is still common in Britain and elsewhere, for the team to be referred to as a Home Nation team. Examples of such usage can also be found in the media in the Republic of Ireland