Translation guide
A group for fans of a celebrity, team, or interest. In Japanese, the most common term is ファンクラブ, but there are also native words and related expressions.
Referring to an official membership-based fan club for a celebrity, artist, sports team, etc.
The standard loanword for 'fan club'. Used for official, often paid membership groups.
I joined her fan club.
A more formal term for a support group, often used for politicians, traditional arts, or local celebrities. Can imply a booster club or supporters' association.
A casual, unofficial group of people who share enthusiasm for something.
The broader community of fans, often online or in a subculture.
ファンクラブ is the default for entertainment fan clubs. 後援会 is used for more formal support groups, like those for sumo stables, politicians, or local performers. Using 後援会 for a pop idol fan club would sound overly stiff.
He formed a local supporters' association.
If you want to say 'my fan club' meaning a group of friends who are fans, ファン仲間 is more natural than ファンクラブ, which implies an official organization.
The local supporters' association is backing his election campaign.
あのアイドルの界隈は情報が早い。
That idol's fandom is quick with information.