An Introduction to Probability Models and Stochastic Processes is a comprehensive textbook that presents the fundamental principles of probability theory and stochastic processes with a strong emphasis on mathematical modeling and real-world applications. The book covers probability distributions, random variables, expectation, conditional probability, Markov chains, Poisson processes, renewal theory, random walks, queuing models, Brownian motion, and continuous-time stochastic processes. It combines rigorous theoretical concepts with practical examples, solved problems, and applications in engineering, computer science, finance, operations research, telecommunications, artificial intelligence, and data analytics. Designed for undergraduate and postgraduate students, researchers, and professionals, this book provides a solid foundation for understanding uncertainty, randomness, and probabilistic modeling in modern scientific and engineering disciplines.