UFC 23: Ultimate Japan 2 was a mixed martial arts event held by the Ultimate Fighting Championship on November 19, 1999 at Tokyo Bay NK Hall in Tokyo, Japan.

UFC 23 was the second UFC event to take place in Tokyo, Japan, where the newly formed PRIDE Fighting Championships were enjoying massive success. UFC 23 was headlined by a Heavyweight Championship Title bout between Kevin Randleman and Pete Williams, held to determine the champion after Bas Rutten's retirement.

The event also featured a four man "Japanese" tournament, held to crown the first ever UFC Japan Champion. The tournament was the first in the UFC since UFC 17, and the last ever tournament held by the UFC. SEG originally intended UFC Japan to be a separate company, run by local promoters, but due to mounting financial problems, a lack of cooperation from Japanese promoters, and the rise of the popular PRIDE and K-1 organizations, the idea was scrapped following UFC 25: Ultimate Japan 3.

UFC 23 was the first UFC event to not see a home video release, as SEG was nearing bankruptcy and struggling to keep the UFC alive through extremely limited pay per view in the US, as well as minor coverage in Brazil and Japan. UFC 23 has now been released as part of a DVD collection (UFC 21–30). It was also the first to feature James Werme who handled backstage interviews.

Anderson da Silva (Portuguese pronunciation: [ˈɐ̃deʁsõ ˈsiwvɐ]; born April 14, 1975) is a Brazilian mixed martial artist. He is the current UFC Middleweight Champion and the promotion's longest reigning champion. With 14 consecutive wins and 9 title defenses, Silva holds the longest winning streak and title defense streak in UFC history.

Silva is ranked as the number one Middleweight in the world by multiple publications, and is the consensus No. 1 pound-for-pound fighter in the world according to ESPN, Sherdog, Yahoo! Sports, MMAFighting.com and other publications. UFC president Dana White has proclaimed Silva as "the greatest mixed martial artist ever."^{[undue weight? – discuss]} Silva is also the last Cage Rage Middleweight Champion and a former Shooto Middleweight Champion. Besides the UFC and Cage Rage, Silva has fought for a number of other MMA promotions including the Pride Fighting Championships, Shooto and Rumble on the Rock.

Although known primarily for his mastery of Muay Thai striking, Silva is also a Brazilian Jiu-Jitsu blackbelt, a rank he earned in 2006 from Antônio Rodrigo Nogueira who follows Gracie Lineage through Carlson Gracie, like Murilo Bustamante and the Brazilian Top Team. He began martial arts training at the age of 14, training Tae kwon do and earning a black belt by the age of 18. He is also a black belt in Judo and a yellow rope in Capoeira.

Chael Patrick Sonnen (pronounced /ˈtʃeɪl ˈsʌnən/; born April 3, 1977) is an American mixed martial artist who competes as a middleweight in the Ultimate Fighting Championship. He was an NCAA Division I All-American wrestler at the University of Oregon, a silver medalist at the 2000 Greco-Roman World University Championships, as well as a two-time Dave Schultz Memorial International Greco-Roman winner.

As of October 2011^[update], Sonnen is ranked as the No. 2 middleweight in the world by Sherdog.

Sonnen was born Chael Patrick Sonnen on April 3, 1977 in West Linn, Oregon.

Sonnen started his MMA career at the age of 19 in 1997 by defeating Ben Hailey in Vancouver, Washington. His second fight was against future ICON Sport Middleweight Champion and Strikeforce Middleweight contender Jason "Mayhem" Miller. Sonnen went 6–0 in his first six fights, until his loss to Trevor Prangley, which he later avenged in 2006 at UFC Ultimate Fight Night 4. He also fought The Ultimate Fighter winner and former UFC Light Heavyweight Champion Forrest Griffin.

Dana White (born July 28, 1969) is the current President of the Ultimate Fighting Championship (UFC), a mixed martial arts organization based in the United States.

Born in Manchester, Connecticut on July 28, 1969, White grew up in Las Vegas, Nevada, Ware, Massachusetts and Levant, Maine. White is a passionate Boston Red Sox fan. During his youth, he bounced back and forth between Boston and Maine. He attended the University of Massachusetts Boston but did not finish; however, while there he did launch a boxing program for inner-city youth.

White has a background as an aerobics instructor. In 1992, White established Dana White Enterprises in Las Vegas. He conducted aerobics classes at three gyms in the Las Vegas area and began managing MMA fighters Tito Ortiz and Chuck Liddell.

While working as a manager, White learned that Semaphore Entertainment Group, the parent company of the UFC, was looking for a buyer for the UFC. White contacted childhood friend Lorenzo Fertitta, an executive at Station Casinos, and a former commissioner of the Nevada State Athletic Commission. Within a month, Lorenzo and his older brother Frank bought the UFC, with White installed as its president. White currently owns about 9% of Zuffa, LLC, the entity the Fertitta brothers created to own and manage the UFC.

Michael Gerard "Mike" Tyson (born June 30, 1966) is a retired American professional boxer. Tyson is a former undisputed heavyweight champion of the world and holds the record as the youngest boxer to win the WBC, WBA and IBF heavyweight titles at 20 years, 4 months and 22 days old. Tyson won his first 19 professional bouts by knockout, with 12 of them occurring in the first round. He won the WBC title in 1986 after defeating Trevor Berbick by a TKO in the second round. In 1987, Tyson added the WBA and IBF titles after defeating James Smith and Tony Tucker. He was the first heavyweight boxer to simultaneously hold the WBA, WBC and IBF titles, and the only heavyweight to individually unify them.

In 1988, Tyson became the lineal champion when he knocked out Michael Spinks in the first 91 seconds of the fight. Tyson successfully defended the world heavyweight championship nine times, including victories over Larry Holmes and Frank Bruno. Tyson lost his titles to 42-to-1 underdog James "Buster" Douglas on February 11, 1990, in Tokyo, Japan, by a knockout in round 10. Tyson continued in his quest to regain the titles, defeating Donovan Ruddock twice in 1991. Tyson was then scheduled to take on the undisputed heavyweight champion Evander Holyfield but pulled out due to injury.