HOAS may refer to:

• Helsingin seudun opiskelija-asuntosäätiö, a student housing provider in Helsinki, Finland
• Higher-order abstract syntax, representing the abstract syntax of a programming language

• Grand Doubletree
• Grand drape
• Grand Ducal Burial Vault
• Grand Ducal consort of Luxembourg
• Grand Ducal consort of Luxemburg
• Grand Ducal consorts of Luxembourg
• Grand Ducal consorts of Luxemburg
• Grand Ducal Council of San Francisco
• Grand Ducal court
• Grand Ducal Gendarmerie
• Grand Ducal Guard
• Grand Ducal Mausoleum
• Grand-Ducal Saxon Art School, Weimar
• Grand-Duche de Luxembourg
• Grand Duchess Alexandra Georgievna (Alexandra of Greece)
• Grand Duchess Alexandra Georgievna (Alexandra of Greece and Denmark)
• Grand Duchess Alexandra Georgievna of Russia
• Grand Duchess Alexandra Iosifovna (Alexandra of Saxe-Altenburg)
• Grand Duchess Alexandra Iosifovna (Alexandra of Saxe-Altenburg
• Grand Duchess Alexandra Petrovna
• Grand Duchess Alexandra Petrovna (Alexandra of Oldenburg)
• Grand Duchess Alexandra Petrovna of Russia
• Grand Duchess Anastasia Nicholaievna Romanova
• Grand Duchess Anastasia Nikolaevich (Anastasia of Montenegro)
• Grand Duchess Anastasia Nikolaevna (Anastasia of Montenegro)