The transmission and distribution of electric power is based on complex interconnected power systems. Every interconnected system can split up into several subsystems due to faults, maloperation or targeted switching. The questions then arise whether these subsystems are survivable, and whether the size of these subsystems are random or predefined, and under which conditions can these isolated subsystems operate in a stable manner. Due to the energy transition, more renewable generation units are installed in the distribution grid, facilitating local intended isolated grids, but also increasing the probability of unintended isolated grids, which must be controlled and dealt with. Though the topic of islanding has been increasingly discussed in academia in recent years, this topic has not yet been comprehensively described in any specialist book. Intended and Unintended Islanding of Distribution Grids addresses this subject, providing a practical reference for researchers at universities and in industry, as well as at grid operators, involved with building, extending or maintaining electricity grids. Chapters cover basics and control of power system dynamics and stability, behaviour at grid connection points, power system restoration, protection, islanding detection, planning methods for secure islanding, modelling for distribution grid analysis in the time-domain, insular power systems, droop based practical examples, practical aspects of bottom-up grid restoration, and unintended islanded grids.