The diesel locomotive combines various physical problems and challenges, requiring interesting technological solutions. Nowadays, most locomotives worldwide are powered by diesel engines. However, a diesel locomotive is a complex vehicle, and even the engine introduced over 100 years ago is still capable of development. Particularly in the last three decades, electronics in almost all components have been updated. Manufacturers like Vossloh and Voith have played a significant role in this. This book aims to provide a clear overview of the central components of a diesel locomotive and their functions.