© 2020 Elsevier LtdThe trend of utilizing renewable energy sources is witnessing a brisk growth around the world. Among the various sources of renewable energy, hydropower is considered the most favorable due to its high potential and distinct advantages such as predictability, high energy density etc. Moreover, to extract the hydrokinetic energy from flowing streams, different designs of hydrokinetic turbines have emerged which operate on a similar principle as the wind turbines. The Savonius turbine is a drag-based device reported to have good starting characteristics, which makes it a fitting choice for hydrokinetic energy extraction, especially in low-velocity flows. However, along the development, it was noted that somehow this turbine has a poor energy conversion efficiency. To overcome this limitation, various design optimization strategies have been proposed. This paper attempts to review the optimization studies of Savonius turbine regarding its probable applications in harnessing hydrokinetic energy. The studies concerning each of the structural parameters influencing the turbine performance are discussed thoroughly. There is hardly any review study available hitherto, which exclusively discusses and summarizes the optimization studies conducted for Savonius design by solely considering water as the operating medium. Hence, the data presented in this study will serve as a basis to understand the existing research on Savonius turbine, thereby enabling researchers to fill the gaps in this area with reference to hydrokinetic applications.