AHD

AHD, a three-letter abbreviation, may refer to:

Linguistic meanings

* "Althochdeutsch" (Old High German) the earliest stage of the German language
* The American Heritage Dictionary of the English Language
** The AHD system (or ) of pronunciation used in this dictionary.

Medical meaning

* Advance Health Directive, an Australian legal document
* Advance health care directive
* Alveolar hydatid disease, a parasitic disease
* Antihypertensive drugs

Others

* Academic Honors Diploma
* Anti-handling device, part of a landmine
* Ashtead railway station, from its National Rail code
* Audio High Density, an audio-only version of the Video High Density videodisc format
* Australian Height Datum