TMJ may refer to:

• Temporomandibular joint connecting the jaw to the skull
  • Temporomandibular joint dysfunction, pain in the jaw
• Ten Mile Junction LRT station, a closed Light Rail Transit station in Singapore (LRT station abbreviation: TMJ)
• Tohoku Mathematical Journal
• The Milwaukee Journal, a forerunner newspaper to the current-day Milwaukee Journal Sentinel
• Tunku Mahkota Johor or the Crown Prince of Johor in Malaysia, currently Tunku Ismail Idris
• Too Much Joy, American alternative rock group
• Total metal jacket bullet, a small-arms projectile
• Termez Airport, Uzbekistan, near the Afghan border (IATA code: TMJ)
• Samarokena language of Indonesian Papua (ISO code: tmj)
• WTMJ (AM), a radio station in Milwaukee, Wisconsin known casually as "TMJ"
• WTMJ-TV, an NBC-affiliated television station in Milwaukee, Wisconsin which utilizes the on-air branding of "TMJ4"