The International Wrestling Grand Prix Heavyweight Championship is the premiere championship in New Japan Pro Wrestling. It was introduced in 1987, when New Japan founder, Antonio Inoki defeated Masa Saito in a tournament final.
In 2005, the title was won by former WWE Champion, Brock Lesnar. In 2006, then-champion Brock Lesnar was stripped of the title for being unable to defend it; however, Lesnar claims he was owed money by NJPW and kept the physical belt. He signed with Antonio Inoki's Inoki Genome Federation (IGF) in 2007, losing the championship to Kurt Angle on the inaugural broadcast. IGF and TNA recognize the championship as legitimate.
New Japan, however, did not recognize this championship as legitimate, and revealed a 4th design for their top belt. They designated Angle's belt the IWGP Third Belt Championship, thus creating a new championship. During this time, Kurt Angle was also the TNA World Heavyweight Champion, being one of the few men to ever hold two World Heavyweight Championships simultaneously.
Angle lost the IWGP Third Belt to Shinsuke Nakamura, holder of the IWGP Fourth Belt, unifying the IWGP Heavyweight Championship.