Modern Blast Furnace Ironmaking - An Introduction (Fourth Edition, 2020) describes the principles of the blast furnace process. As a starting point, the blast furnace is seen as a simple iron ore melter, while gradually the physical, chemical and metallurgical background of the blast furnace process is clarified. The book focuses on the control of the process with respect to thermal control, gas flow control and casthouse operation. In this book, all essential process details are described and a special focus is on cost optimization by low coke rates and on management of the process in case of disturbances and upsets. The optimization of the blast furnace is not only based on "best practice transfer", but also requires conceptual understanding why a measure works in some cases and not in other cases. In other words, operational improvement is not only based on know-how, but as well on know-why. This publication can be used as an introductory text for students of metallurgy as well as for blast furnace operators and management.