GT 64: Championship Edition is a racing video game for the Nintendo 64. It was released in Japan as City Tour GrandPrix: Zen Nihon GT Senshuken with two new Japanese Exclusive tracks in 1998. Hence its title, it was an official licensed game to All-Japan GT Championship, featuring cars and drivers of the 1997 season. GT and Grand Tour are references to long distance traveling such as in the traditional version of the Grand Tour. It was the final game ever published by Ocean Software.
Despite the name, it is otherwise unrelated to Kaneko's Hyper Battle Game: Zen Nihon GT Senshuken. Instead, it is related to Imagineer's GT Racing.
Source: Wikipedia, "GT 64: Championship Edition", available under the CC-BY-SA License.