Particle dynamics with aggregation and fragmentation occurs in almost every branch of science and engineering. Examples include the formation of stars and planets in astrophysics, the formation of colloids and polymers in chemistry, the formation of raindrops and snowflakes in meteorology, the formation of fuel sprays in mechanical engineering, impact damage to aircraft and satellites in aerospace engineering, and drilling and blasting in civil and mining engineering. This is one of the first textbooks to give particle dynamics with aggregation and fragmentation a full treatment, putting it on an equal footing with fluid dynamics and solid mechanics. To help readers understand the connections to fluid dynamics, this book shows how particle dynamics occurs in ideal gases, granular gases, and fluid turbulence. Instead of relying on empirical results that apply only under specific circumstances, the book uses broad physical principles such as conservation of mass, momentum, and energy. The text draws on rigorous mathematical theory and modern high-performance computing, while avoiding the complex details. The book also provides extensive references for those readers who need them. While intended for a graduate level audience, the book is written in a graphically-rich style which will be accessible to advanced undergraduates. In particular, it includes over 100 figures and over 200 examples, most of which are placed into grey boxes to avoid interrupting the main text. While surveying the relevant research literature, this book also draws on the author's unique insights into particle aggregation and fragmentation, gained from participating in relevant research and development activities in industry and academia for over 25 years.