In Ireland, commonly referred to as the Republic of Ireland, vehicle registration plates are the visual indications of motor vehicle registration – officially termed "index marks" – which it has been mandatory since 1903 to display on most motor vehicles used on public roads in Ireland. The alphanumeric marks themselves are issued by the local authority in which a vehicle is first registered.

A vehicle registration plate, also known as a number plate, license plate or licence plate, is a metal or plastic plate or plates attached to a motor vehicle or trailer for official identification purposes. The registration identifier is a numeric or alphanumeric code that uniquely identifies the vehicle within the issuing authority's database. In Europe most countries have adopted a format for registration plates that satisfies the requirements in the Vienna Convention on Road Traffic, which states that cross-border vehicles must display a distinguishing code for the country of registration on the rear of the vehicle. This sign may be an oval sticker placed separately from the registration plate, or may be incorporated into the plate. When the distinguishing sign is incorporated into the registration plate, it must also appear on the front plate of the vehicle, and may be supplemented with the flag or emblem of the national state, or the emblem of the regional economic integration organisation to which the country belongs. An example of such format is the common EU format, with the EU flag above the country code issued in EU member states.