An International Vehicle Registration Code (formerly International Registration Letter or International Circulation Mark) is a distinguishing letter, or combination of letters, that is typically displayed on a white oval plate or sticker attached to the rear of a motor vehicle to enable the country in which it is registered to be readily identified. For this reason they are (with certain exceptions, as explained below) obligatory on all vehicles which cross international frontiers; however, the codes do not have to be displayed by vehicles circulating solely within their country of original registration, unless otherwise required by the registering authorities in those countries.

Some countries incorporate an oval plate into the design of their standard number plates, while all member states of the European Union allow vehicles equipped with "Europlates" (that is to say, plates which include a vertical blue stripe at their left-hand end displaying the EU stars and the member state's country code) to dispense with a separate oval. This dispensation also extends to countries in the European Economic Area (EEA) and to others which have signed the Vienna Convention on Road Traffic.

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