The G1 (Grade One) Climax is a professional wrestling tournament held each August by the New Japan Pro-Wrestling (NJPW) promotion. Though it has sometimes been held as a single-elimination tournament, it is usually (and currently) held as a round-robin, with winners from two blocks wrestling in the final to decide that year's winner. In its current format, the tournament lasts four weeks. The winner of each block is determined by a points system; two points for a victory, one point for a draw, and zero points for a loss.
NJPW had an annual tournament since 1974 under various names: the World League (1974–1977, based on the World (Big) League tournament from the old Japanese Wrestling Association held between 1959 and 1972); the MSG League (1978–1982); the International Wrestling Grand Prix (IWGP) League (1983–1988; although the first winner, Hulk Hogan, was awarded a championship belt, this is not the beginning of the IWGP Heavyweight Championship). Most of these tournaments were dominated by NJPW's founding top star Antonio Inoki. In 1989, there was a World Cup Tournament, which included wrestlers from the then-Soviet Union. No tournament was held in 1990.
With Inoki's dominance over NJPW gone, the promotion established the G1 Climax tournament in 1991 as a platform to showcase the company's top heavyweights and have them compete in round-robin matches where the winners of the two divisions would then square off in the tournament finals. NJPW's then president Seiji Sakaguchi named the tournament after the G1 horse race. Though considered a continuation of the previous tournaments, officially NJPW does not recognize the earlier tournaments as part of the G1 Climax lineage. The first G1 was held from August 7 to August 11, 1991, at Tokyo's Ryōgoku Kokugikan. The winner of the tournament, assuming they are not already the champion, has traditionally earned a shot at the IWGP Heavyweight Championship. Since 2012, the winner has earned the "Tokyo Dome IWGP Heavyweight Championship challenge rights certificate", a contract for a title shot at NJPW's largest event, Wrestle Kingdom in Tokyo Dome, held annually on January 4. Much like WWE's Money in the Bank contract, the certificate is kept in a briefcase that the wrestler then has to defend until the end of the year. Since its inception, the contract has never changed hands in these matches. In 2015, the tournament format was changed with NJPW reducing the number of G1 Climax matches per show, giving the participating wrestlers more time to rest between matches. This increased the tournament's length to four weeks.