Who is known for composing the first known mass?

Guillaume de Machaut is recognized for composing the first known mass, specifically his "Messe de Nostre Dame," which dates back to the 14th century. This work stands out as one of the earliest examples of a complete setting of the Ordinary of the Mass, showcasing the transition from Gregorian chant to polyphonic music. Machaut's mass is significant not only for its musical innovation but also for its textual and liturgical structure, which laid the groundwork for future mass compositions during the Renaissance and beyond.

The other individuals mentioned played important roles in the development of music but did not compose the first known mass. Claudio Monteverdi was pivotal in the early Baroque period with his operas and secular music. Johann Sebastian Bach, while influential in the realm of sacred music with his cantatas and Passions, came much later in music history. Pope Gregory the Great is traditionally associated with the organization of Roman chant but not with the composition of a mass.