Which 14th-century composer wrote the 'Messe de Nostre Dame', the first complete polyphonic mass?

Guillaume de Machaut wrote the Messe de Nostre Dame, the earliest complete setting of the Mass Ordinary attributable to one composer. Machaut was both a French poet and composer, and the work was composed before 1365 during the 14th century.

The mass contains six movements: Kyrie, Gloria, Credo, Sanctus, Agnus Dei, and Ite, missa est. It is written for four voices, an unusually substantial texture for its period, and demonstrates the intricate polyphonic style associated with medieval music. Polyphony means that multiple independent vocal lines sound together rather than moving as a single melody.

Machaut served as a canon at Reims Cathedral, where the mass was probably intended for a Lady Mass, although its exact original performance circumstances remain uncertain. Scholars have also debated how closely its movements were conceived as a unified cycle, but its stylistic coherence was historically influential.

The wording “first complete polyphonic mass” needs a little care. Earlier compilations, including the Tournai Mass, contain polyphonic settings of Mass movements, but those sections are believed to have been written independently by different composers. Machaut’s importance lies in creating the earliest complete Ordinary credited to a single composer—not necessarily the first polyphonic mass music of any kind.