LJ may refer to:

  • Sierra National Airlines' IATA code
  • LJ, the sequent calculus of Gentzen's for intuitionist logic
  • LiveJournal
  • Linux Journal
  • La Jolla, California
  • Library Journal
  • Lightweight Java
  • Ljubljana, the capital of Slovenia
  • LaserJet
  • Lord Justice of Appeal (plural: LJJ)
  • Larry Johnson (basketball, born 1969)
  • Lawrence Jackson, USC defensive lineman
  • Larry Johnson (American football)
  • LJ Reyes
  • LJ Create
  • Lennard-Jones potential, a function used in chemical physics
  • Lemon Jelly, a British electronica duo
  • Lashkar i Jhangvi, Muslim terrorist organization

Read more about LJ:  Fictional Characters