Shale oil is an important component of China's national energy strategy. Research on onshore and offshore shale oil in China is advancing in parallel, and investigating the rock mechanical properties of oil shale is fundamental to achieving efficient shale oil exploration and development. In this study, Chang 7 oil shale from the Yanchang Formation in the Ordos Basin and the second member of the Liushagang Formation (Liu 2) oil shale from the Weixinan Sag were selected as research targets. A comprehensive investigation of their physical and mechanical properties was conducted from the perspectives of rock strength, anisotropy, microstructure, failure characteristics, and hydration behavior. The mechanical characteristics of the oil shales were clarified, and the similarities and differences between onshore and offshore oil shales were analyzed. The results show that: (1) Both oil shales exhibit pronounced anisotropy, and rock strength varies systematically with bedding angle. The Liu 2 oil shale has more developed bedding and stronger anisotropy than the Chang 7 oil shale. (2) Anisotropy significantly affects failure modes. Shear failure occurs at a bedding angle of 60°, whereas splitting failure dominates at 90°. The influence of anisotropy on failure is more evident for the Liu 2 oil shale. (3) The Chang 7 oil shale exhibits higher strength than the Liu 2 oil shale. However, Chang 7 oil shale is more susceptible to hydration, showing a greater degree of strength degradation after hydration. These findings provide technical support for wellbore stability studies and hydraulic fracturing design.