"Ach wie flüchtig, ach wie nichtig" (Ah how fleeting, ah how insubstantial) is a German Lutheran hymn with lyrics by Michael Franck, who published it with his own melody and a four-part setting in 1652. Johann Crüger's reworked version of the hymn tune was published in 1661. Several Baroque composers used the hymn, including Johann Sebastian Bach, who wrote a chorale cantata. It is part of the current Protestant hymnal Evangelisches Gesangbuch, and has also been used by 20th-century composers such as Ernst Pepping and Mauricio Kagel.