The geological guide by Kurt Mohr on the Harz, western part, is now available in its 5th edition. Since the 4th edition, numerous works on the geology of the Western Harz and its immediate surrounding areas have been published. A selection of the most important research findings has been incorporated into the text of this guide. The bibliography has been expanded by about 50 citations. In the meantime, the volume on the Harz, eastern part with Kyffhäuser crystalline, covering the geology and rocks in the eastern part of the Harz, has also been published. In the new edition, the established excursion routes remain largely the same. Additionally, over ten new outcrops have been integrated into the route descriptions, resulting in a total increase of 20 pages. May the 5th edition of this guide also inspire geological excursions in the western part of this highly interesting German low mountain range. The excursions provide an overview of the geology, mineralogy, and mining history of the Western Harz. Like previous editions, the book will guide professional geologists, students, and the general public in understanding the geology of the Harz. The guide is divided into a general section and explanations of the excursions. The general section offers a brief overview of geological research in the Western Harz and highlights the deposits (geology and mineral deposits of the Harz) as well as the geographical and hydrological conditions. The overall Harz is addressed whenever a broader perspective is required.