This paper reports on the mechanical properties of fused silica flexures manufactured by a two-step process combining femtosecond lasers exposure below the ablation threshold and chemical etching. Flexural strengths as high as 2.7 GPa were measured, demonstrating that femtosecond lasers can be efficiently used to produce arbitrarily shaped high-strength mechanical devices, opening new opportunities for the design of monolithically integrated optomechanical devices.