The 1st Formula One race
Devotees of the sport will know what I mean by calling the 1950 British Grand Prix the first formula one race, even though it was by no means the first Grand Prix. GP races date back to the Edwardian era, the first Grand Prix, appropriately enough, being the 1906 French GP. There was also an occasional US GP event, held on Long Island(!) and called the Vanderbilt Cup(!!)).
The FIA formally codified a set of rules, for formula one, formula two, and formula three in the late 1940s, so that a still devastated European economy could have a formal, unified world championship(i.e. a European championship, but we'll call it a world championship) in which the regulations for fuel capacity, engine size, etc, were codified and made comparatively uniform-- and the premier series was called formula one, with the championship race at Silverstone, England, on May 13th, 1950, inaugurating the first season.