The IWGP Junior Heavyweight Championship is a professional wrestling junior heavyweight championship owned by the New Japan Pro Wrestling (NJPW) promotion. "IWGP" is the acronym of NJPW's governing body, the International Wrestling Grand Prix. The title was introduced on February 6, 1986 at an NJPW show. Only wrestlers under the junior heavyweight weight-limit may hold the championship. NJPW currently controls two junior heavyweight championships: the IWGP Junior Heavyweight Championship and the IWGP Junior Heavyweight Tag Team Championship. The weight limit for the tag team title is 220 lb; it is assumed that this title has the same weight limit. From August 5, 1996 until November 5, 1997 the title was part of the J-Crown, or J-Crown Octuple Unified Championship. The J-Crown was an assembly of eight different championships from several different promotions. It was created on August 5, 1996 when The Great Sasuke won an eight-man tournament. The IWGP Junior Heavyweight Championship, the British Commonwealth Junior Heavyweight Championship, the NWA World Junior Heavyweight Championship, the NWA World Welterweight Championship, the UWA World Junior Light Heavyweight Championship, the WAR International Junior Heavyweight Championship, the WWA World Junior Light Heavyweight Championship, and the WWF Light Heavyweight Championship were the eight championships that were involved. On November 5, 1997, then-champion Shinjiro Otani vacated all J-Crown belts but the IWGP Junior Heavyweight Championship after the World Wrestling Federation (WWF) retook control of its Light Heavyweight title, effectively ending the J-Crown. Being a professional wrestling championship, the title is won as a result of a predetermined outcome.
Reigns 36 and 37 occurred on World Championship Wrestling's Nitro television broadcast when Juventud Guerrera defeated Jushin Liger on November 29, 1999, and on December 6, 1999 when Liger retrieved the championship by defeating Guerrera's stand-in Psychosis. The inaugural champion was Shiro Koshinaka, who defeated The Cobra on February 6, 1986 in the finals of a tournament. Liger holds the record of most reigns, with 11. At 628 days, Liger's sixth reign is the longest in the title's history. Liger, with a combined 11 reigns, holds the record for most days as champion at 2,245. Guerrera's only reigns hold the record for shortest reign at one week. With 11 successful defenses, Minoru Tanaka's reign under the ring name "Heat" had the most during a single reign. Over his 11 reigns, Liger successfully defended the title 31 times, the most of any champion. With zero, El Samurai's second reign, Hiroshi Hase's second reign, Tiger Mask IV's fourth and sixth reigns, Liger's fourth reign, Guerrera's only reign, and Pegasus Kid's only reign are all tied for least successful defenses. Guerrera and Pegasus Kid are the only champions to not successfully defend the title once.
- Champion history - History of the wrestlers who have held the belt.
- Title matches - Matches in which the title was defended.