UDT may refer to:
Organisations Uitgeverij De Tijd, a former Belgian publisher Underwater Demolition Team, United States Naval reconnaissance and amphibious landing beach demolition unit from which the U.S. Navy SEALs evolved Republic of Korea Navy UDT/SEAL, from the Republic of Korea Navy União Democrática Timorense, (Timorese Democratic Union), a conservative political party in East Timor Union Démocratique Tchadienne, (Chadian Democratic Union), the second African political party in Chad Union Djiboutienne du Travail (Union of Djibouti Workers), a trade union centre in Djibouti United Dominions Trust, a subsidiary of the former Trustee Savings Bank, merged with Lloyds Bowmaker in 2001 Union démocratique du travail, a left-wing Gaullist party
Computing UDP-based Data Transfer Protocol, a high-performance data transport protocol and library User-defined type, in computer science that is generally synonymous with "record", "structure", "composite type" or "class"
Technology Urine Diversion Toilet, a toilet system where urine and faeces are separated at source
Measurement Underdeck tonnage, a unit of measurement of a ship's weight