List of motorways in the United Kingdom

The list of motorways in the United Kingdom is a complete list of motorways in the United Kingdom. Note that whilst one numbering scheme is used for Great Britain, roads in Northern Ireland are allocated their own numbers on an ad hoc basis.

Former motorways
Roads which used to be motorways but have been downgraded:

Motorways under construction or planned
Following the completion of the M74 and M80 motorways in 2011 and the A1(M) Dishforth to Leeming extension in 2012, no motorways are under construction in the United Kingdom save for the short approach roads to the Forth Replacement Crossing which will form part of the M90.

The only other new motorway constructions currently being planned in the UK are the 6 mile M8 Baillieston to Newhouse completion project, the A1(M) Leeming - Barton upgrade and a motorway running south of the city of Newport, south Wales. This motorway remains to be properly named, only being described as the M4 relief road.

Unbuilt motorways
There have been many plans for motorways in the UK that have not been built. Below is a list of plans that were not built (not exhaustive):
 * M12 in 3 forms:
 * From the London end of the M11 to Brentwood;
 * From the London end of the M11 to Maplin Sands Airport (also not built);
 * From the M25 (in the vicinity of the M11) to Chelmsford.
 * M13, from East London to Maplin Sands airport passing south of Southend.
 * M17 Castle Donington bypass, a short spur off the M1;
 * M31, a bypass of the busiest section of the M25, cutting the corner for traffic from the West.
 * M59, M58 junction 2 to south of Preston.
 * M64, between the M6 south of Stoke-on-Trent and the M1 near Derby. Mostly built as the A50.
 * M601, which would have entered Manchester from the M62 (now the M60) in the Irwell Valley at Clifton near Pendlebury.
 * M650, Airedale Motorway from near Silsden to Shipley.
 * A6(M) (or M66 extension), which would have formed an eastern bypass for Stockport. As of March 2006, this is still under the planning stage as part of the SEMMMS (south east Manchester multi modal study) project (though not as motorway).
 * A556(M), which would have cut the corner between the M6 and M56 near Warrington.
 * Chippenham Spur, off the M4
 * Strensham – Solihull motorway, a link between the M50 and M42 or M69

Many cities had urban motorway plans, most of which were not built. London, Newcastle, Liverpool, Manchester/SELNEC and Glasgow all had extensive plans.

Unbuilt motorways
The following motorways were planned, but never built.
 * M11, from the M1 going through Lisburn and then crossing the M1 again and ending at Newry
 * M23, from the M2 to Derry

There were also urban motorway plans for Belfast