The theory of micropolar fluids is a significant and simple generalization of the theory of the classical Newtonian viscous fluid whose equations of motion are given by the conventional Navier- Stokes equations. Physically these fluids represent fluids consisting of rigid randomly oriented particles suspended in a viscous medium. The theory of couple stress fluids provides for the polar effects such as sustenance of couple stresses and body couples in a continuum medium. The micropolar fluid model takes into account both the mechanical interactions as well as the microstructure of molecules within a fluid volume element. The couple stress fluid model takes into consideration the mechanical interactions taking place across a surface and it is not concerned with the micro structure. Though, in a way, the micropolar fluid theory is more general than the couple stress fluid theory. This book provides the good knowledge on the theory of Fluid Mechanics especially on the theory of micropolar and couple stress fluids for professionals, researchers and Scientists.