Judah ben David Hayyuj (Hebrew: יְהוּדָה בֶּן דָּוִד חַיּוּג׳, romanized: Yəhuḏā ben Dawiḏ Ḥayyuj, Arabic: أبو زكريا يحيى بن داؤد حيوج, romanized: Abū Zakariyya Yahyá ibn Dawūd Ḥayyūj) was a Maghrebi Jew of Al-Andalus born in North Africa. He was a linguist and is regarded as the father of Hebrew scientific grammar.
Judah was born in Fez, then part of the Fatimid Caliphate, about 945. At an early age, he went to Córdoba during the Golden age of Jewish culture in Spain, where he seems to have remained till his death about 1000. He was the first to propose that Hebrew words stem from triconsonantal roots.