The Great Britain road numbering scheme is a numbering scheme used to classify and identify all roads in Great Britain. Each road is given a single letter and a subsequent number. Though this scheme was introduced merely to simplify funding allocations, it soon became used on maps and as a method of navigation. There are two sub-schemes in use: one for motorways, and another for non-motorway roads.

The main roads in Northern Ireland are signed "M"/"A"/"B" as in Great Britain. Whereas the roads in Great Britain are numbered according to a zonal system, there is no available explanation for the allocation of road numbers in Northern Ireland, though their numbering is separate from the system in England, Scotland and Wales.