8D

8D or 8-D may refer to:


 * Eight-dimensional space
 * "Grinning with glasses", an emoticon in which the "8" represents open eyes and the "D" an open mouth, see List of emoticons
 * Eight disciplines problem solving

Transport

 * 8D Technologies, a Canadian company that develops bicycle-sharing systems
 * GCR Class 8D, a class of British 4-4-2 steam locomotive
 * Secondary State Highway 8D (Washington), former name of Washington State Route 141
 * Typ 8D, first-generation Audi A4

IATA airline codes

 * Astair
 * Expo Aviation
 * Servant Air