London Underground’s circular red-and-blue symbol is called the roundel.
The design consists of a horizontal blue bar crossing a red ring. London Underground adopted the symbol in the early 20th century, and it became a highly recognizable sign for stations, maps, vehicles and publicity. Its simple shape lets passengers identify the network quickly in busy streets and transport hubs.
The roundel developed from earlier transport branding associated with London’s Underground Electric Railways Company. Edward Johnston’s influential typeface was later used with the symbol, helping create the consistent visual identity associated with the Underground.
Although commonly called the “Tube logo,” roundel is the more precise name for the symbol itself. Similar roundels have been used by other parts of Transport for London, often with different colors to identify services such as buses, trams or London Overground. The red ring and blue bar are especially associated with the Underground.