This textbook offers a journey through the complex world of turbulent flows, beginning with their physical characteristics and progressing through the mathematical foundations of fluid dynamics. Readers will explore the transition to turbulence, spectral analysis, and the Kolmogorov theory, gaining insight into the nature and behavior of turbulent structures. The book then delves into advanced modeling techniques, including URANS and LES methodologies, addressing the closure problem and presenting various turbulence models from zero-equation to hybrid approaches. With detailed theoretical formulations, practical case studies, and exercises throughout, this comprehensive resource equips students, researchers, and engineers with the tools to understand, simulate, and analyze turbulent flow phenomena in both academic and applied contexts.