HDL may refer to one of the following:

Science and technology[edit]

• Hardware description language, in computer engineering
• Handle System identifier (Hdl.handle.net)
• High-density lipoprotein, complex particles
• Huntington's disease-like syndromes, a family of genetic neurological diseases

Other uses[edit]

• GE HDL, a diesel engine
• HDL System, HDL Universal Tactical role-playing game system produced by Tremorworks, LLC
• Harry Diamond Laboratories, a U.S. Army laboratory
• Headstone Lane railway station (National Rail station code), London, England
• Les Hurlements d'Léo, an alternative rock band from France