Systems and methods for monitoring wind turbine loading are provided. In one embodiment, a system includes a main shaft, a bedplate, and a gearbox coupled to the main shaft and mounted to the bedplate. The gearbox includes an outer casing and a torque arm extending from the outer casing. The system further includes an isolation mount coupled to the torque arm, and a sensor configured to measure displacement of the torque arm. In another embodiment, a method includes operating the wind turbine, and detecting displacement of a torque arm of a gearbox of the wind turbine. The method further includes calculating a moment for a main shaft of the wind turbine based on the displacement of the torque arm.