A semiconductor package includes a substrate including an upper surface and a side surface, an adhesive layer disposed on an edge of the upper surface of the substrate, and a stiffener including a horizontal portion disposed on the adhesive layer and extending in an horizontal direction to an outside of the substrate in a plan view and a vertical portion connected to the horizontal portion and extending vertically downwards from the horizontal portion. The vertical portion is spaced apart from the side surface of the substrate with a vertical gap extending in a vertical direction therebetween, and the outer width of the stiffener is 40 mm or more.