Provided is a bone plate and a bone plate system optimized for hybrid HTO. The bone plate of the present invention includes a body portion (1a) to be fixed to an obliquely anterior medial surface of the tibia (X) below the osteotomy surface in the tibia (X), the body portion extending in a longitudinal direction of the tibia； a wide portion (1b) wider than the body portion (1a) and to be fixed to an outer peripheral surface of the tibia (X) at a higher position than the osteotomy surface； a connecting portion (1c) that connects the body portion (1a) and the wide portion (1b)； and a plurality of screw holes (4, 4a, 4b, 4c) arrayed in the body portion (1a), the wide portion (1c) and the connecting portion (1c). An inner surface that extends from the wide portion (1b) to the connecting portion (1c) and faces the tibia (X) has a continuous curved shape twisted about an axis along the longitudinal direction of the tibia (X). The wide portion (1b) is offset in an outward plate thickness direction with respect to the body portion (1a). When the bone plate is attached to the tibia (X), a curvature of a side surface of the connecting portion (1c) that follows the posterior surface of the tibia (X) is larger than a curvature of a side surface of the connecting portion (1c) that follows the anterior surface of the tibia (X).
