A Mass of Life (German: Eine Messe des Lebens) is a piece of choral music by English composer Frederick Delius, based on the German text of Friedrich Nietzsche's philosophical novel Thus Spoke Zarathustra. In 1898, Delius had written a male choir and orchestral setting of "Midnight Song" from the same work, and this was revised to form part of the Mass. A Mass of Life is the largest of Delius's concert works, written for four SATB soloists, double choir and orchestra. It was dedicated to Fritz Cassirer, who had had an important hand in choosing the passages from Nietzsche's text.