Li0.33La0.57TiO3 (LLTO) is a potential Li-ion conducting membrane for use in aqueous Li-air batteries. To be in this configuration its mechanical properties must be determined. Dense LLTO was prepared using a solid-state (SS) or sol-gel (SG) procedure and was hot-pressed to yield a high relative density material (> 95 %). Young's modulus, hardness, and fracture toughness of the LLTO-SS and sol-gel LLTO-SG materials was determined and compared to other solid Li-ion conducting electrolytes. The Young's modulus for LLTO-SG and LLTO-SS was 186 +/- A 4 and 200 +/- A 3 GPa, respectively. The Vickers hardness of LLTO-SG and LLTO-SS was 9.7 +/- A 0.7 and 9.2 +/- A 0.2 GPa, respectively. The fracture toughness, K (IC), of both LLTO-SG and LLTO-SS was similar to 1 MPa m(1/2); the fracture toughness of LLTO-SG was slightly higher than that of LLTO-SS. Both LLTO-SG and LLTO-SS have a Young's modulus and hardness greater than the other possible solid Li-ion conducting membranes; Li7La3Zr2O12 and Li1+x+y Al (x) Ti2-x Si (y) P3-y O-12. Based on modulus and hardness hot-pressed LLTO exhibits sufficient mechanical integrity to be used as a solid Li-ion conducting membrane in aqueous Li-air batteries but, its fracture toughness needs to be improved without degrading its ionic conductivity.