Many methodologies have been developed for plant-wide control (PWC) of chemical processes. However, not much attention has been paid to the systematic classification of these methodologies. Such a classification is essential in order to better understand and improvise these methodologies. Thus, one of the main objectives of this work is to review and classify the existing PWC methodologies. Accordingly, the PWC methodologies developed to-date are systematically classified and briefly discussed. Secondly, considering the importance of and the attention received by the reactor-separator-recycle (RSR) process in the PWC literature, RSR control methodologies and studies are reviewed. Next, various methods for determining control degrees of freedom are discussed, followed by a discussion on the industrial processes considered in the reported PWC studies. Finally, a brief review of the different performance measures used in PWC system validation is presented. The classification and reviews presented in this paper will be of interest to those working on and/or applying PWC methodologies.