The Quasi-one-dimensional flow: An Introduction grew out of Masters Project by the same title first presented in 2005 and repeated with modifications for publication in peer referred Journal of Mathematical theory and Modeling. The objective is to present the subject of Quasi-one-dimensional flow to an audience unfamiliar with all but the most basic numerical techniques and to do so in such a way that it would become clear to everyone. This “The Quasi-one-dimensional flow” book is truly a handbook for beginners. The book is divided into two parts. The author lays out the subject in Part I by first defining the terms, Next, he describes the theoretical foundations of the fluid flows. This includes the governing equations of fluid dynamics, concentrating on their mathematical properties which contain the keys to the choice of the numerical approach and finally the Method of discretizing the equations is discussed and transformation techniques and grids are presented. Part II is devoted to application example material. It provides insight into the steps needed to obtain a numerical solution of a flow field using the Finite difference technique and the Mac Cormack’s Method.