TID or tid may refer to:

• Thermionic detector, a detector used in gas chromatography based on the principle of ionization and measuring a change in electron flux
• Total ionizing dose (related to ionizing radiation)
• Transient ischemic dilation, a finding on a nuclear cardiology test consistent with coronary artery disease
• TID class tug, a British tugboat design of World War II
• TID (musician) – a musician from Tanzania
• Traffic identifier – an identifier used for traffic flows in 802.11 wireless local-area networks
• ter in die, Latin for three times daily; usually refers to prescription medication dosage (e.g. TID)
• Tag identification memory, in a Gen 2 RFID tag, this consists of memory about the tag itself, such as the tag ID
• Transportation improvement district
• Travelling Ionospheric Disturbance – a type of Ionospheric perturbation
• Truncated dodecahedron
• Travel itinerary directory
• Tobacco Induced Diseases – a peer reviewed journal