The engineering-oriented field of open channel hydraulics is based on the fluid mechanics principles of hydromechanics but typically employs simplified one-dimensional flow approaches. The present textbook, "Introduction to Open Channel Hydraulics," is suitable for students in civil and environmental engineering programs. It includes a detailed description of the turbulent flow characteristics of open channel flows and the associated engineering approaches to flow resistance in open channels, the consideration of highly non-uniform flow, and the related control structures, as well as facilities for energy dissipation. It also explains slightly non-uniform flow with approaches for the numerical calculation of water surface levels in rivers and channels under steady conditions. The final chapter is dedicated to unsteady flow processes, including periodic waves, surge and drawdown movements, as well as gradually varying flood waves.