Jar can mean:

• Containers:
  • Antique fruit jar
  • Canopic jar, used in ancient Egyptian burial
  • Leyden jar, a simple capacitor
  • Killing jar
• JAR (file format) is a file format used to package Java programming language applications
• Jar, Norway, a centre in the municipality of Bærum
• JAR is the jamming avoidance response, which is shown by electric fish
• Jewish Autonomous Region of Russia
• Jars, Cher, in the French département of Cher
• The Jar, a webcomic
• J.A.R., a song by Green Day