Four-Inch Course is a road-racing circuit first used for the 1908 Tourist Trophy Race for racing automobiles. The races were held on public roads closed for racing by an Act of Tynwald (the parliament of the Isle of Man). The name of the course derives from the regulations for the 1908 Tourist Trophy adopted by the Royal Automobile Club which limited the engines of the competing automobiles to a cylinder diameter of four inches. The Four-Inch Course was adopted by the Auto-Cycle Club for the 1911 Isle of Man TT Races.