Ji or ji may refer to:
- Ji (surname) (姬), the surname of the Zhou dynasty
- Ji (surname) (吉, 己, &c.), other Chinese surnames
- Ji, variant romanizations of surnames written Chi (e.g., 池) or Zhi (e.g., 智) in pinyin
- The State of Ji ( 薊國, 蓟国), a city-state in northern China during the Shang and Zhou dynasties
- Ji (city), the capital of Ji and its successor Yan within modern Beijing, China
- Ji province:
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- Jì (冀), the character abbreviation for Hebei, China
- Jí (吉), the character abbreviation for Jilin, China
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- Ji County:
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- Ji County, Shanxi (吉县) in Linfen
- Ji County, Tianjin (蓟县)
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- -ji, a suffix denoting respect in the Indian subcontinent
- ji (字), a Japanese courtesy name
- ji (halberd) (戟), a kind of Chinese halberd
- ji (flute) (지, 篪), an ancient Korean bamboo flute
- Ji Koizumi, a character in the anime Guru Guru Pon-chan
- Ji (magazine), a Ukrainian cultural magazine
- Ji (film), a Tamil film starring Ajith and Trisha Krishnan
- Ji (album), an album by English singer Junior Giscombe
JI may refer to:
- Jemaah Islamiyah, the militant Islamic organization
- Midway Airlines (JI) IATA code
- Journal of Infection, an academic journal
- Joint Implementation, one of the flexible mechanisms of the Kyoto Protocol
- Journal Inquirer, a Connecticut newspaper
- Jakobshavn Isbræ, a glacial outlet in Greenland
- Jurong Institute, a now-defunct pre-university institution in Singapore