Every IWGP Heavyweight Champion (IGF) (2005-2008)

The IWGP Heavyweight Championship (IWGPヘビー級王座, IWGP hebī-kyū ōza) was a professional wrestling world heavyweight championship owned by New Japan Pro-Wrestling (NJPW) that existed from 1987 until 2021. This article covers the interpretation of the title's history according to Inoki Genome Federation (IGF) and its founder Antonio Inoki. Both promotions agreed on the title's history up to July 15, 2006, when Brock Lesnar, who was the reigning champion, was stripped of the title by NJPW. Inoki saw this event as an error made by NJPW and spawned the IGF version of the title's history, with Lesnar still recognized as the official champion.

IGF was a territory of the National Wrestling Alliance (NWA), thus the title was additionally recognized by the NWA as the NWA Japan Championship. NJPW recognized the title as the IWGP 3rd Belt (IWGP Third Belt, IWGP 3rdベルト, IWGP sādo beruto),[a] a championship that was merely represented by a previous (third) version of the IWGP Heavyweight Championship's title belt. The title also saw the involvement of Total Nonstop Action Wrestling (TNA), which also recognized it as the IWGP World Heavyweight Championship.[3] TNA assisted in the title's retirement in 2008 when TNA wrestler Kurt Angle lost to Shinsuke Nakamura to unify Angle's IGF title with Nakamura's NJPW-recognized IWGP Heavyweight Championship. The NJPW-recognized IWGP Heavyweight Championship was retired in 2021.

As a professional wrestling championship, the title was won via a scripted ending to a match or awarded to a wrestler because of a storyline. All title changes occurred at IGF- or NJPW-promoted events. There were a total of three reigns among three wrestlers during the title's brief history.