A lateral force estimation system provided in a vehicle that has a plurality of wheels and turns in a tilted posture with respect to a ground surface, comprising: a lateral acceleration detector configured to detect lateral acceleration at a predetermined position of the vehicle; a roll angular acceleration detector configured to detect roll angular acceleration of the vehicle; a yaw angular acceleration detector configured to detect yaw angular acceleration of the vehicle; a roll angle detector configured to detect a roll angle of the vehicle; a storage configured to store a position of a center of gravity of the vehicle and a mass of the vehicle; a ground surface position lateral acceleration calculator configured to calculate acceleration exerted in a direction perpendicular to a front-and-rear direction of the vehicle and parallel to a ground surface at an intersection position of a straight line passing through a center of gravity of the vehicle and parallel to a top-and-bottom direction of the vehicle with the ground surface as ground surface position lateral acceleration based on the lateral acceleration detected by the lateral acceleration detector, the roll angular acceleration detected by the roll angular acceleration detector, the yaw angular acceleration detected by the yaw angular acceleration detector, the roll angle detected by the roll angle detector, and the position of the center of gravity of the vehicle stored in the storage; and a vehicle lateral force calculator configured to calculate a sum of lateral forces exerted on the plurality of wheels as a vehicle lateral force based on the roll angle detected by the roll angle detector, the roll angular acceleration detected by the roll angular acceleration detector, the position of the center of gravity and mass of the vehicle stored in the storage, and the ground surface position lateral acceleration calculated by the ground surface position lateral acceleration calculator. a lateral acceleration detector configured to detect lateral acceleration at a predetermined position of the vehicle; a roll angular acceleration detector configured to detect roll angular acceleration of the vehicle; a yaw angular acceleration detector configured to detect yaw angular acceleration of the vehicle; a roll angle detector configured to detect a roll angle of the vehicle; a storage configured to store a position of a center of gravity of the vehicle and a mass of the vehicle; a ground surface position lateral acceleration calculator configured to calculate acceleration exerted in a direction perpendicular to a front-and-rear direction of the vehicle and parallel to a ground surface at an intersection position of a straight line passing through a center of gravity of the vehicle and parallel to a top-and-bottom direction of the vehicle with the ground surface as ground surface position lateral acceleration based on the lateral acceleration detected by the lateral acceleration detector, the roll angular acceleration detected by the roll angular acceleration detector, the yaw angular acceleration detected by the yaw angular acceleration detector, the roll angle detected by the roll angle detector, and the position of the center of gravity of the vehicle stored in the storage; and a vehicle lateral force calculator configured to calculate a sum of lateral forces exerted on the plurality of wheels as a vehicle lateral force based on the roll angle detected by the roll angle detector, the roll angular acceleration detected by the roll angular acceleration detector, the position of the center of gravity and mass of the vehicle stored in the storage, and the ground surface position lateral acceleration calculated by the ground surface position lateral acceleration calculator.