This textbook explores both the theoretical foundations of the Finite Volume Method (FVM) and its applications and implementation in Computational Fluid Dynamics (CFD) codes. Readers will discover a thorough explanation of the FVM numerics and the algorithms used for the simulation of incompressible and compressible fluid flows, along with an examination of the various components needed to develop state-of-the-art solvers. Two particular CFD codes are explored. The first of these codes is uFVM, a three-dimensional unstructured pressure-based finite volume program, implemented within Matlab as an academic CFD tool. The second CFD code which this book elaborates on is the OpenFOAM® library, an open source framework that can be used to develop a range of CFD solvers for the simulation of industrial scale problems.The work covers details of all the topics necessary for the development of a robust CFD code for the simulation of fluid flow at all speeds within the framework of the collocated unstructured finite volume method. Over 220 figures are included to assist the reader’s understanding of concepts and algorithms, along with numerous examples and more than a hundred exercises on FVM numerics, programming, and applications. This book is useful at many levels and is suitable to be used for an introductory course on the FVM, for an advanced course in numerics, and as a reference for CFD programmers and researchers.