The Dietel manuscript, D-LEb Peters Ms. R 18, also known as the Dietel Collection and, in German, Choralsammlung Dietel, is the oldest extant manuscript with a large collection of four-part chorales by Johann Sebastian Bach. It contains 149 of Bach's chorale harmonisations (not 150 as is written on its title page) and originated around 1735. The music in the manuscript was copied by Johann Ludwig Dietel, one of Bach's pupils from the Thomasschule.[1][2][3][4]