Tendon consists of soft collagen, yet it is mechanically strong and firmly adhered to the bone owing to its hierarchically anisotropic structure and unique tendon-to-bone integration (enthesis), respectively. Despite the recent advances in biomaterials, hydrogels simultaneously providing tendon-like high mechanical properties and strong adhesion to bone-mimicking enthesis is still challenging. Here, a strong, stiff, and adhesive triple-network (TN) anisotropic hydrogel that mimics a bone-adhering tendon is shown. The tough adhesive TN hydrogel is developed by combining imidazole-containing polyaspartamide (providing multiple hydrogen bonds to the bone surface) and energy-dissipative alginate-polyacrylamide double-network. To mimic the anisotropic structure and high mechanical properties of tendons, the bone-adhered TN hydrogel is linearly stretched and subsequently fixed via secondary cross-linking. The resulting hydrogel exhibits high tensile modulus and strength while maintaining a high bone adhesion without chemical modification of the bone surface. Furthermore, a bone-ligament-bone structure with strong bone adhesion reminiscent of the natural ligament is realized.