The gravitational fields of galaxies are a major influence on light rays reaching the earth from the corners of the universe, and the images obtained by telescopes of the night sky. A complete and consistent study of the effects of the gravitational fields produced by massive astrophysical bodies requires recourse to Einstein's general theory of relativity. To this end, an analysis is presented of the behaviour of light rays in the relativistic gravitational field of rotating, pressure free, ideal fluid disks. These disks are models for rotating galaxies whose fluid particles are the individual stars comprising the galaxy in question. The stars interact with one another solely via the gravitational force. The main results in this thesis include: (1) Visualisation of rotating galaxies in curved spacetime (2) The gravitational deflection of individual light rays (3) Gravitational lensing (multiple images, caustics etc.)