Lake Ontario, the smallest in surface area among the Great Lakes, is the last lake in the Great Lakes' hydrologic chain. In this study, Lake Ontario's marine renewable energy resources are characterized. The historical wave records reveal up to 8 m significant wave heights in Lake Ontario's eastern basin. Furthermore, the lake's historical water level data indicate that storm surges can get as large as 1 m near Port Weller and Burlington. The storms of November 13, 2003, and January 30, 2008, are estimated to produce a total theoretical potential energy of ~25 GWh. The lake-wide monthly mean wave power for the selected year 2011 is at its peak in October and November, exceeding 10 kW/m. On the other hand, it is estimated to be around 1 kW/m during late spring and summer. The present work is part of an extensive study attempting to characterize marine renewable energy resources for the entire Great Lakes and follows the recently published works on Lake Erie and Lake Michigan (Farhadzadeh et al., 2017; Velioglu Sogut et al., 2018). It is also the first study elaborating on the characterization of Lake Ontario's marine renewable energy resources.