Hucbald (born c. 840, Tournai?, Fr.—died 930, Saint-Amand, near Tournai) was a medieval French musical theorist, scholar, and humanist.
Hucbald was a pupil of his uncle, the scholar Milo of Saint-Amand; mention of him is found at Nevers, Saint-Amand, Saint-Omer, and Reims. Hucbald was an abbot and apparently spent his life teaching. His treatise De harmonica institutione describes the gamut (the series of recognized musical notes) and the eight modes. He also wrote poems, metrical prayers, and hymns.
Hucbald was long believed to be the author of other theoretical works now attributed to an unidentified writer known as Pseudo-Hucbald, who lived somewhat later. Some scholars speculate that his works may in fact have several authors. These theoretical works are of great importance. The Musica enchiriadis and Scholia enchiriadis give the earliest written description of music in several voices: parallel organum, in which a plainchant melody is sung in parallel fourths or parallel fifths. De alia musica deals with a notational system called daseian notation. Although it never became generally accepted, it was an early attempt to show exact pitch in musical notation; it used symbols showing 18 specific pitches and placed the words to be sung in a set of horizontal lines.