IRA is an acronym with various meanings.

There are several paramilitary groups which claim the title 'Irish Republican Army', and advocate an all-island Irish state achieved through force with no ties to the United Kingdom.

• Irish Republican Army (explaining the linked history of movements claiming to be the IRA)
• Old IRA: The IRA was the name adopted as the armed section of the self-declared Irish Republic (1919-1922). Fought the Anglo-Irish war, later split between "regulars" (became the Irish army) and "irregulars" (became the OIRA).
• Official IRA: Marxist IRA officially on ceasefire since the 1970s. The PIRA (below) broke from this movement in 1969, INLA broke away in 1974.
• Provisional Irish Republican Army: The PIRA somtimes called the Provos. Formed in 1969 (split from OIRA) associated with Sinn Féin, it is the dominant republican group.
• Continuity Irish Republican Army: A breakaway from the PIRA formed in 1986 by those angry with the route being taken by the Adams leadsership in the PIRA and Sinn Fein.
• Real Irish Republican Army: A breakaway from the PIRA formed after the 1990s ceasefires.

On a completely different note, there is also:

• The Individual Retirement Account (legal name: Individual Retirement Arrangement) or IRA, a private retirement account in the USA that enjoys certain tax benefits.

There is also:

• Ira (which has a number of alternative meanings)