UDR may refer to: Ulster Defence Regiment, a former British Army infantry regiment Universal dielectric response, An emergent scaling behaviour in heterogeneous materials under alternating current União Democrática Ruralista, a Brazilian right-wing association of farmers Union of Democrats for the Republic, a former political party in France Union for Democracy and the Republic (Chad), a political party in Chad Democratic Union for the Republic, a former political party in Italy UDR, Inc., a real estate company in the United States Udaipur Airport, Indian airport (IATA airport code) Untethered dead reckoning, GNSS-assisted dead reckoning without external sensors User-Defined Reductions in OpenMP U.D.R., Brazilian comedy rock band. Univision Deportes Radio, a Spanish language sports radio network in the United States. See also Udr or Uðr, one of the Nine Daughters of Ægir in Norse mythology Umpire Decision Review System (UDRS)