This textbook is a comprehensive introduction to the field of discrete event systems, emphasizing breadth of coverage and accessibility of the material to a large audience of readers with different backgrounds. Its key feature is the emphasis placed on a unified modeling framework for the different facets of the study of discrete event systems. This modeling framework is centered on automata and to lesser extent on Petri nets and is gradually refined: untimed models for logical properties concerned with the ordering of events, timed models for properties that involve timing considerations, and stochastic timed models for properties that involve a probabilistic setting. The unified modeling framework transcends specific application areas and allows linking of the following topics in a coherent manner for the study of discrete event systems: language and automata theory, supervisory control, Petri net theory, \((\max, +)\) algebra, Markov chains and queueing theory, discrete-event simulation, perturbation analysis, and concurrent estimation techniques.