  While the origin of r-process nuclei remains a long-standing mystery, recent
spectroscopic studies of extremely metal-poor stars in the Galactic halo
strongly suggest that it is associated with core-collapse supernovae. In this
article, an overview of the recent theoretical studies of the r-process is
presented with a special emphasis on the astrophysical scenarios related to
core-collapse supernovae. We also review a recent progress of the Galactic
chemical evolution studies as well as of the spectroscopic studies of extremely
metal-poor halo stars, which provide us important clues to better understanding
of the astrophysical r-process site.
