Shinjiro Otani (大谷晋二郎, Ōtani Shinjirō; born July 21, 1972) is a Japanese semi-retired professional wrestler and the current acting president of Pro Wrestling Zero1 (Zero1). He is currently inactive from pro-wrestling competition due to a cervical spine injury sustained in April 2022. A product of the New Japan Pro Wrestling (NJPW) dojo, Otani is best known for his longtime association with Zero1, a promotion he founded in 2001 along with Shinya Hashimoto.

Starting his career in NJPW as a junior heavyweight, Otani gained a reputation as a gutsy underdog and would go on to hold several championships during his nine-year run with the promotion, including the IWGP Junior Heavyweight Championship and the J-Crown, as well as forming a successful tag team with dojo classmate Tatsuhito Takaiwa, twice holding the IWGP Junior Heavyweight Tag Team Championship. After jumping to the heavyweight division in 2001, Otani would leave New Japan the same year, joining Shinya Hashimoto as one of the founders of Pro Wrestling Zero1 (Zero1). Following the departure of Hashimoto in 2004, Otani was pushed as one of the promotions top stars, becoming a six time Intercontinental Tag Team Champion, a one time World Heavyweight Champion and a four-time winner of the Fire Festival. In addition to his role as a wrestler, Otani has also served as acting company president since 2007.

Otani was born in Yamaguchi and was a big pro wrestling fan during his youth, specifically Antonio Inoki's New Japan Pro Wrestling (NJPW). He attended the only two events NJPW ran in Yamaguchi yearly and idolised Kengo Kimura. At one point during his childhood, he snuck into a hotel in a bid to try and meet Antonio Inoki; initially stopped by security, they allowed him in upon Inoki's instruction, who signed Otani's "闘魂" (fighting spirit) hachimaki, after which the young Otani vowed to Inoki that he would one day make it to NJPW. Otani was successful in amateur wrestling during high school.

Upon graduation, Otani planned to move almost 600 miles from Yamaguchi to Tokyo to join a professional wrestling dojo. Otani's dream was strongly opposed by his parents, which resulted in him running away from home in January 1992 at the age of 19, leaving for Tokyo with only between ¥50,000-¥60,000 of otoshidama money to his name. After being homeless for a brief period of time, Otani finally found a place to stay, a small tatami-like dwelling for ¥24,000, located next to a public toilet and without a futon to sleep on.

At the time, the only wrestling school Otani knew of was Animal Hamaguchi's dojo, where he would travel and introduce himself to Hamaguchi. Hamaguchi accepted Otani into his dojo where he began his training, in addition to feeding him and getting Otani a part-time job in a local liquor store, which allowed him to pay for better living quarters. Hamaguchi brought Otani to the NJPW dojo in February 1992 and he enrolled soon after, training in the same class as Tatsuhito Takaiwa and Yuji Nagata. As part of his rookie duties, Otani would also spend two years working closely with Shinya Hashimoto as his assistant, which led to the two developing a long-lasting friendship.

Otani made his in-ring debut on June 25, 1992, losing to Hiroyoshi Yamamoto at a house show in Fukushima. His televised debut came a little under a month later, losing to Osamu Nishimura in Gifu. Otani spent much of 1992 and 1993 trading wins and losses with fellow dojo classmates such as Tatsuhito Takaiwa, Tokimitsu Ishizawa and Yuji Nagata, customary for younger wrestlers in Japan as they develop and earn their place within the company. He became known for his springboard dropkick, his corner face wash, and developed a reputation as a likeable underdog thanks to his sympathetic performances and his willingness to challenge senior wrestlers, in particular Jushin Thunder Liger. The two met for the first time on May 25, 1993, in a Top of the Super Juniors tournament match in Korakuen Hall, with Liger victorious. Otani would struggle throughout his first foray into the tournament, failing to advance past the first stage but managing to earn a solitary win over Eddie Guerrero in Hamamatsu.

Otani represented NJPW during their feud with Wrestle Association-R (WAR) on January 16, 1994, losing to Masao Orihara at a WAR's Super Revolution event. He would once again enter the renamed Best of the Super Juniors tournament that summer and performed much better, defeating the likes of Taka Michinoku and Black Tiger, however also once again losing to Jushin Liger and failing to advance to the finals. In October, he partnered up with Wild Pegasus for the Super Grade Junior Heavyweight Tag League. The two would reach the semi-finals on October 18, beating Dean Malenko and Tokimitsu Ishizawa to book their place in the final, where they defeated Black Tiger and The Great Sasuke in a highly acclaimed bout to win the tournament, giving Otani his first taste of success in the company. His strong performances throughout 1994 earned him his first IWGP Junior Heavyweight Championship opportunity on October 30, however, he was unable to overcome champion Norio Honaga and lost by referee's decision at Ryogoku Kokugikan. He received a big opportunity at the annual "Dream Win" card on October 30, where he was defeated by Keiji Muto, one of the top stars of New Japan in a singles match.

Otani won the first championship of his career on December 13, 1994, beating Norio Honaga to win the UWA World Welterweight Championship. After two successful defences, he dropped the title to IWGP Junior Heavyweight Champion Koji Kanemoto in a double title match on April 16 in Hiroshima. Otani would turn his attention to the Best of the Super Juniors tournament in June where he would have his best outing to date, making it all the way to the final where he was narrowly defeated by former partner Wild Pegasus.