An Alp is a supernatural being in German folklore.
"Nachtmahr" ("Night-mare"), by Johann Heinrich Füssli (1802), depicts an Alp sitting on the sleeper's chest, with a mara staring through the background.
German folklore is the folk tradition which has developed in Germany over a number of centuries. Seeing as Germany was divided into numerous polities for most of its history, this term might both refer to the folklore of Germany proper and of all German-speaking countries, this wider definition including folklore of Austria and Liechtenstein as well as the German-speaking parts of Switzerland, Luxembourg, Belgium, and Italy.
Illustration of Hansel and Gretel, a well-known German folktale from the Brothers Grimm, by Arthur Rackham, 1909