A seatbelt webbing includes an auxetic portion elongated along an axis. The auxetic portion includes a plurality of segments rotatably connected to each other at hinges. The hinges are spaced along the axis and are transverse to the axis. The auxetic portion includes a plurality of strands. Each strand is embedded in at least two of the hinges. When tensile force above a predetermined level is applied to the auxetic portion by a vehicle occupant, e.g., the chest of the vehicle occupant, the auxetic portion both stretches along the axis and widens transverse to the axis, i.e., has a negative Poisson ratio.