Ludwig van Beethoven composed his first-ever mass setting in 1807, to a commission from Prince Nikolaus II Esterházy: the Mass op. 86 for soloists, chorus and orchestra. The occasion was the celebration of the name day of the Prince’s wife. In the temporal proximity of such famous works as the Fourth Piano Concerto, the Violin Concerto, and the Fourth and Fifth Symphonies, he here created a work of an entirely different nature. He informed his publisher that he believed he had treated the text of the Mass “like it has seldom been treated”. This study score reproduces the full musical text of the Beethoven Complete Edition. The sources consulted for this edition are presented in detail in the preface and the critical report.