A1(M) is the designation given to a series of four separate motorway sections in the UK. Each section is an upgrade to a section of the A1, a major north–south road which connects London, the capital of England, with Edinburgh, the capital of Scotland. The first section, the Doncaster Bypass, opened in 1961 and is one of the oldest sections of motorway in Britain. Construction of a new section of A1(M) between Leeming and Barton was completed on 29 March 2018, a year later than the anticipated opening in 2017 due to extensive archaeological excavations. Its completion linked the Barton to Washington section with the Darrington to Leeming Bar section, forming the longest A1(M) section overall and reducing the number of sections from five to four.

The A1, also known as the Great North Road, is the longest numbered road in the United Kingdom, at 410 miles (660 km). It connects London, the capital of England, with Edinburgh, the capital of Scotland. The numbering system for A-roads, devised in the early 1920s, was based around patterns of roads radiating from two hubs at London and Edinburgh. The first number in the system, A1, was given to the most important part of that system: the road from London to Edinburgh, joining the two central points of the system and linking the UK's (then) two mainland capital cities. It passes through or near north London, Hatfield, Welwyn Garden City, Stevenage, Baldock, Letchworth Garden City, Biggleswade, Eaton Socon, Buckden, Peterborough, Stamford, Grantham, Newark-on-Trent, Retford, Doncaster, Pontefract, York, Wetherby, Ripon, Darlington, Durham, Gateshead, Newcastle upon Tyne, Morpeth, Alnwick and Berwick-upon-Tweed.