Hydromorphone, a more common synonym for dihydromorphinone and dimorphone, commonly a hydrochloride (trade names Palladone, Dilaudid, and numerous others) is a potent centrally-acting analgesic drug of the opioid class. It is a derivative of morphine, to be specific, a hydrogenated ketone thereof and, therefore, a semi-synthetic drug. It is, in medical terms, an opioid analgesic and, in legal terms, a narcotic. It should not be confused with hydromorphinol, also known as 14-hydroxydihydromorphine and RAM-320, or dihydromorphine (Paramorfan). While all of these are strong opioids, they are indeed different drugs. Additional confusion arises from the fact that, in a handful of countries, hydromorphinol is distributed under the trade name Numorphan, which is the trade name for oxymorphone in the rest of the world, according to the current version of The A-Z Encyclopaedia of Alcohol & Drug Abuse and other references.

Hydromorphone is known in various countries around the world by the trade names Hydal, Sophidone, Hydrostat Hydromorfan, Hydromorphan, Laudicon, Hymorphan, Opidol, Palladone and others. An extended-release version of hydromorphone called Palladone was available for a short time in the United States before being voluntarily withdrawn from the market after a July 2005 FDA advisory warned of a high overdose potential when taken with alcohol. As of March 2010, it is still available in the United Kingdom under the brand name Palladone SR, and in most other European countries. Another extended-release version called Hydromorph Contin, manufactured as controlled-release capsules, continues to be produced and distributed in Canada by Purdue Pharma Inc. of Pickering, Ontario. The newest extended-release preparation (and the first to last 24 hours - see below) is Jurnista, made by Janssen-Cilag. In addition to Purdue-Frederick and Janssen-Cilag, manufacturers of hydromorphone products include Knoll, Abbott, Endo, Mallinckrodt, Merck, Mundipharma, and Lannacher, among others.

Hydromorphone is used in medicine as an alternative to morphine for analgesia, and as a second- or third-line narcotic antitussive (cough suppressant) for cases of dry, painful, paroxysmal coughing resulting from continuing bronchial irritation after influenza and other ailments, inhalation of fungus, and other causes. In general, it is considered the strongest of the antitussive drugs, and was developed shortly after diacetylmorphine was removed from clinical use for this purpose in most of the world and banned outright in many countries. The effectiveness of hydrocodone as an antitussive may be partly due its being partially converted to hydromorphone in the liver.