Hydroxy can refer to:
- In chemical nomenclature, the prefix "hydroxy-" shows the presence of a hydroxyl functional group (-OH)
- An abbreviation for the medication hydroxyzine, which is commonly sold under the brand names Atarax, Ucerax, Serecid, and Vistaril
- Hydroxy gas: A nickname for oxyhydrogen, a combination of hydrogen and oxygen gas produced from the electrolysis of water