This book introduces stochastic processes with emphasis on their applications in science, engineering, finance, computer science, and operations research. Self-contained, it builds the foundation of modeling time-dependent random phenomena in these areas and illustrates applications with practical examples. Numerous exercises reinforce the concepts and techniques discussed and allow readers to assess their understanding. Solutions to most of the exercises are provided in an appendix. While focused primarily on practical aspects, the presentation includes some important proofs along with more challenging examples and exercises for those more theoretically inclined.