Spanning energy regimes from ultracold atoms to plasma chemistry, this concise volume presents a unified treatment of termolecular reaction dynamics, integrating statistical models, direct three-body recombination, and classical mechanisms such as Lindemann-Hinshelwood. With applications ranging from atmospheric ozone formation to hydrogen combustion and ion solvation, the book bridges theory and experiment across chemical physics, physical chemistry, and molecular dynamics. Each chapter critically evaluates theoretical frameworks against experimental data, highlighting open questions and future directions. Designed for postgraduate students and researchers, this accessible yet rigorous text consolidates decades of scattered literature into a single, authoritative resource. Written by Jesus Perez-Rios, a leading figure in molecular reaction theory, this volume is essential reading for anyone seeking to understand or model complex reaction pathways in gas-phase chemistry.