This third edition of Malcolm Longair's highly acclaimed textbook is an up-to-date text on astrophysical cosmology expounding the structure of classical cosmological models from a contemporary viewpoint. This forms the background to a detailed study of the origin of structure and galaxies in the Universe. The derivations of many of the most important results are described using simple physical arguments which illuminate the results of more advanced treatments. A very wide range of recent observational data is brought to bear upon the problems, including the results from the Hubble Space Telescope, the Planck mission of the European Space Agency, galaxy surveys such as the Sloan Digital Sky Survey, the ALMA submillimetre observatory, studies of Type 1a supernovae and many other remarkable recent observations. This book serves as an ideal text for graduate level courses on astrophysical cosmology and is also highly appreciated as a reference source for professional astrophysicist and cosmologists.