UFC 25: Ultimate Japan 3 was a mixed martial arts event held by the Ultimate Fighting Championship on April 14, 2000 at the Yoyogi National Gymnasium in Tokyo, Japan.

The event was the third UFC event to be held in Japan. UFC 25 was headlined by a fight between Tito Ortiz and Wanderlei Silva, held to determine the new Light Heavyweight Champion following Frank Shamrock's retirement from the UFC. The Octagon announcer was local Sanshiro Matuyama instead of the regular Bruce Buffer.

The event featured the first UFC appearance of future UFC Middleweight Champion Murilo Bustamante, as well as future PRIDE fighter Ikuhisa Minowa. This event also contained an interview with John Perretti, the UFC matchmaker prior to his replacement, the famous Dana White.

UFC 25 was initially seen live on pay-per-view. Many years later, UFC 25 was finally released as part of a DVD collection (UFC 21–30).

Cain Velasquez Ramirez (born July 28, 1982) is a Mexican American mixed martial artist fighting in the Ultimate Fighting Championship where he is a former UFC Heavyweight Champion. He is a two-time All-American collegiate wrestler from Arizona State University in Tempe, Arizona, and a Junior College National Champ at Iowa Central Community College. He is a two-time 5A state champion in Arizona, compiling a record of 110–10 for Kofa High School in Yuma, Arizona. Cain Velasquez is ranked #2 in the heavyweight division.

Velasquez, a Mexican American, was born on July 28, 1982 in Salinas, California to Efrain and Isabel Velasquez. Velasquez's father, Efrain, came from Mexico to the United States illegally. Efrain met his wife Isabel, married her, and gained US citizenship. Velasquez has two siblings, Efrain, Jr., and Adela. He was raised in Yuma, Arizona. He graduated from Kofa High School, where he compiled a record of 110–10 in four years of wrestling, including winning the 5A Arizona Wrestling Championship twice. Velasquez also played football for three years. As a senior, he served as Captain of both his wrestling and football teams.

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.

Joshua Joseph Thomson (born September 21, 1978) is an American mixed martial arts fighter training with American Kickboxing Academy. He has fought in Japan's PRIDE Fighting Championships and America's UFC, as well as Strikeforce and the World Fighting Alliance. Thomson is a former Strikeforce World Lightweight Champion.

Thomson started out very strongly in his MMA career winning his first two professional bouts, before going to a no contest with Norifumi Yamamoto. Thomson would then go on to win his next three fights, including a win over former WEC Lightweight Champion Rob McCullough.

Thomson made his debut in the UFC at UFC 44 defeating Gerald Strebendt by knockout in the first round. He would then pick up a decision victory over Hermes Franca in an incredible fight at UFC 46, before falling victim in his next fight to a highlight reel KO finish at the hands and foot of Yves Edwards.

Thomson was 2-1 in the UFC and 7-1(1) overall before leaving the UFC and opting instead to go overseas to Japan and fight once for PRIDE FC. He won his single fight in PRIDE by submission in the 1st round. Thomson then signed with Strikeforce and would lose his debut fight with the company (a fight for the vacant Strikeforce Lightweight Championship to Clay Guida) but would then go on to win his next six fights, including victories over Duane Ludwig and Nam Phan and would earn another shot at the Strikeforce Lightweight Championship.

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.