JA, Ja, or ja may refer to:

  • Ja, grammatical particle meaning "yes" in most Germanic languages, e.g. German (including informal English)
  • Ja in Slavic languages means I
  • Jamaica
  • JA, a platform of vehicles made by Chrysler
  • Jane's Addiction, the American alternative rock band
  • Japan, Nato country code
  • Japanese language, ISO 639-1 alpha-2
  • Jasmonic acid
  • JoomlArt, Professional Joomla Template/Extension Club
  • Judge Advocate
  • Judge of Appeal
  • Junior Achievement
  • B&H Airlines, IATA airline designator JA
  • The Cyrillic letter Я, also known as ya
  • Ja, is the unit of measurement of length in Korea.

JA is the name of:

  • Ja Rule, an American rapper
  • Jonathan Avildsen, known as JA ONE
  • JA (TV series) Danish television show

JA may also refer to:

  • Japan Agricultural Cooperatives, in Japan
  • British Rail Class 73/0 electro-diesel locomotives. Pre-TOPS classification JA
  • Jackson County, Kansas, whose two-letter code on Kansas license plates is JA
  • Jamiat Ahle Hadith a political party in Pakistan