This list is of fatal accidents on the Isle of Man TT Mountain Course used for the Isle of Man TT races, Manx Grand Prix and Classic TT races. The TT Course was first used as an automobile road-racing circuit for the 1908 Tourist Trophy event for racing automobiles, then known as the Four Inch Course. For the 1911 Isle of Man TT race motor-cycle races, the event was moved from the St John's Short Course to the Four Inch Course by the UK Auto-Cycle Club, and became known as the Isle of Man TT Mountain Course, or TT Course, when used for motorcycle racing.