Mobile21
| Native name | モバイル21株式会社 | 
|---|---|
| Romanized name | Mobairu21 kabushiki gaisha | 
| Company type | Joint venture | 
| Industry | Video game | 
| Founded | October 7, 1999 | 
| Defunct | December 14, 2002 | 
| Fate | Defunct | 
| Headquarters | Asakusabashi, Tokyo, Japan | 
| Key people | Yoneoka (president) | 
| Owners | 
Mobile21 Co., Ltd. was a Japanese video game developer that was a 50/50 joint venture between Nintendo and Konami established in October 1999. Mobile21 primarily concentrated on creating Game Boy Advance games, with a particular focus utilizing the mobile phone linking features of the Mobile Adapter GB accessory. The company was led by Masaki Yoneoka and its headquarters were located within Nintendo's offices in the Asakusabashi district of Tokyo.