|Presumed Origin||the Kabuki-mono|
|Actual Number||86 300 members|
|Activities||Blackmail, Illegal gambling, Casino, Prostitution, Smuggling|
Daimon of the Yamaguchi-gumi
|Founded by||Harukichi Yamaguchi|
|Territory||Primarily based in Kobe but has territory all over Japan, including in Tokyo|
|Ethnicity||Japanese, Korean Japanese|
|Criminal activities||illegal gambling, assassinations, bid rigging, extortion, drug trafficking, Internet pornography, loansharking, money laundering, murder, sōkaiya, prostitution, securities fraud, arms trafficking, and infiltration of legitimate businesses|
|Allies||Affiliated gangs such as the Yamaken-gumi, Kodo-kai, Takumi-gumi, Goto-gumi, Kokusui-kai, Yamasai-kai and more|
|Rivals||Has had conflicts with other Yakuza groups such as Sumiyoshi-kai and the Ichiwa-kai|
It is one of the largest criminal organizations in the world. Estimates put the number of active members at just over 45,000, with thousands more having strong associations. It is, by far, the largest of the boryokudan groups, and its membership encompasses roughly 45% of the 86,300 yakuza in the Japanese underworld. Formal members of the Yamaguchi-gumi are 102 total people; 1 kumicho, 15 shatei (younger brother) and 86 wakachu (child) as of November 2005.
The Yamaguchi-gumi are among the world's wealthiest gangsters, bringing in billions of dollars a year from extortion, gambling, the sex industry, guns, drugs, and real estate and construction kickback schemes. They are also involved in stock market manipulation and Internet pornography.
The Yamaguchi-gumi has its headquarters in Kobe, Japan, but it operates all across Japan and has overseas operations in Asia and the United States. Despite more than a decade of police crackdowns, their numbers have been growing. Its current kumicho (Boss), Shinobu Tsukasa, has declared an expansionist policy - even making inroads into Tokyo, traditionally not Yamaguchi turf.
When Taoka inherited the title of kumicho, it was merely a local family with only dozens of members. It was Taoka who made Yamaguchi-gumi the world's largest criminal organization. He urged his underlings to have legitimate businesses and allowed them to have their own family, which became a kind of subsidiary family of Yamaguchi-gumi. He also created a structural system in the family. Wakagashira were elected as underbosses to the kumicho and some of powerful members were elected as wakagashira-hosa (deputy underbosses).
After the death of Taoka, the heir apparent wakagashira Kenichi Yamamoto (kumicho of the Yamaken-gumi) was serving a prison sentence. He died of liver failure shortly afterward. Fumiko Taoka, Kazuo Taoka's wife, stepped forward to fill the leadership void until a new kumicho could be selected by a council of eight top-level bosses.
In 1984, the elders chose Masahisa Takenaka (kumicho of the Takenaka-gumi) to be the fourth kumicho of Yamaguchi-gumi. One of the other contenders, Hiroshi Yamamoto (kumicho of the Yamahiro-gumi), broke away from Yamaguchi-gumi with many of its powerful members and more than 3,000 of its soldiers to form the Ichiwa-kai. A bitter rivalry existed between the two groups, which led to an all-out war (the Yama-Ichi War) after the Ichiwa-kai's 1985 assassination of Takenaka and wakahashira Katsumasa Nakayama. During the war, acting-kumicho Kazuo Nakanishi (kumicho of the Nakanishi-gumi) and wakagashira Yoshinori Watanabe (kumicho of the Yamaken-gumi) briefly took the leadership role until 1989.
The Yama-Ichi War ended with retirement of Hiroshi Yamamoto which was arbitrated by one of the most respected bosses Seijo Inagawa. After that, the clan elected wakagashira Yoshinori Watanabe as 5th kumicho of the organization. Masaru Takumi (kumicho of Takumi-gumi) was elected as wakagashira. He was so powerful and respected within the organization that his influence overshadowed that of kumicho to some extent.
In 1997, then powerful wakagashira Masaru Takumi was assassinated by underlings of then wakagashira-hosa (deputy underboss) Taro Nakano. After this assassination, they were unable to choose a new wakagashira for more than eight years. As a result, leadership of the organization became weaker. Finally, in 2005, wakagashira-hosa Shinobu Tsukasa (then kumicho of Hirota-gumi) was chosen as new wakagashira and shortly afterward, in August 2005, Tsukasa inherited the position of the 6th kumicho of the Yamaguchi-gumi.
Watanabe has retired to private life — rather uncommon in their world, as bosses usually do not retire until their death. Under Tsukasa's leadership, the 6th Yamaguchi-gumi has resumed expansion. Seiji Takayama, kumicho of Kodo-kai, was elected as wakagashira. They absorbed the Tokyo-based gang Kokusui-kai, thus acquiring lucrative turf in the capital. Tsukasa was imprisoned in December 2005, and is serving a six-year sentence.
Immediately after the Kobe Earthquake of 1995, the Yamaguchi-gumi started a large-scale relief effort for the earthquake victims, helping with the distribution of food and supplies. This help was essential to the Kobe population, because official support was inconsistent and chaotic for several days. 
On April 17, 2007, Tetsuya Shiroo, a senior ranking member of the Suishin-kai (an affiliated Yakuza family to the Yamaguchi-gumi), assassinated Iccho Itoh, the mayor of Nagasaki, over an apparent dispute over damage done to Shiroo's car at a public works construction site. On May 26, 2008, Tetsuya Shiroo was sentenced to death. However, the Fukuoka High Court revoked the death sentence and sentenced him to life imprisonment on September 29, 2009.