Hucbald (Hucbaldus, Hubaldus) (c. 840 or 850 – June 20, 930) was a Frankish music theorist, composer, teacher, writer, hagiographer, and Benedictine monk. Deeply influenced by Boethius' De Institutione Musica, he wrote the first systematic work on western music theory, aiming at reconciling through many notated examples ancient Greek music theory and the contemporary practice of the more recent so-called 'Gregorian chant'.
Born in Northern France, about 850, his name reveals that he could have been closely related to the Carolingian dynasty (he was a familiar of Charles the Bald's court, to whom he dedicated poetical works and luxurious manuscripts). He studied at Elnone Abbey (later named Saint-Amand Abbey, after its 7th-century founder) where his uncle Milo was chief master of studies (scholasticus), in the diocese of Doornik. Hucbald made rapid progress in the sciences of the quadrivium, including that of practical music, and, according to a laudatory 11th-century biographical account, at an early age composed a hymn in honour of St Andrew, which met with such success as to excite the jealousy of his uncle. It is said that Hucbald in consequence was compelled to leave St Amand and to seek protection from the bishop of Nevers.