  Giant radio sources (GRSs) defined to be > 0.7 Mpc are the largest single
objects in the Universe and can be associated with both galaxies (GRGs) and
quasars (GRQs). They are important for understanding the evolution of radio
galaxies and quasars whose sizes range from pc to Mpc scales and are also
valuable probes of their environment. These radio-loud active galactic nuclei
(RLAGN) interact with the interstellar medium of the host galaxy on small
scales and the large-scale intracluster or intergalactic medium for the GRSs.
With several new and sensitive surveys over the last few years, the number of
known GRSs has increased many fold which has led a resurgence of interest in
the field. This review article summarises our current understanding of these
sources based on nearly five decades of research and discusses the importance
of the Square Kilometer Array (SKA) in addressing some of the outstanding
questions.
