ABC was the name of several motorcycle manufacturers located in France, England, and Germany.
There were at least three British firms producing ABC motorcycles including machines designed by Granville Bradshaw. The best known were produced by Sopwith between 1919 and 1922 and although of quite advanced design proved unreliable and eventually caused the company's downfall. A derivation of the Sopwith machine was built under licence at a Gnome & Rhone factory in France with rather more success.
The All British Engine Company, Ltd. of London, United Kingdom was founded in 1912. Later, the name was changed to A.B.C. Motors, Ltd. The company owner was Ronald Charteris and the chief engineer was Granville Bradshaw. They built a variety of A.B.C. engine types until the end of WWI.