悬吊系统亦称为悬挂系统、悬载系统 (Suspension，中国俗称「底大杠」)，乃是一种由弹簧、减震筒和连杆所构成的车用系统，用于连接车辆与其车轮。悬吊系统扮演双重的角色－让车辆的操控和煞车合乎良好的动态安全与操驾乐趣，并保持车主的舒适性及隔绝适当的路面噪音、弹跳与震动。这些特性通常都是互相牵制的，因此悬吊的调整就必须找到两者兼顾的位置。悬吊系统同时也保护车辆本身、或车上的货物行李等，避免这些东西损坏或磨耗。一台车辆的前轮与后轮悬吊设计有可能会大不相同。

这篇条目主要是有关四轮（或多轮）车辆的悬吊。若需要两轮车辆悬吊的相关数据，可参阅悬吊 (机车)、单车悬吊。

This article is primarily about four-wheeled (or more) vehicle suspension. For information on two-wheeled vehicles' suspensions see the motorcycle suspension, motorcycle fork, bicycle suspension, and bicycle fork articles.

Suspension is the system of tires, tire air, springs, shock absorbers and linkages that connects a vehicle to its wheels and allows relative motion between the two. Suspension systems serve a dual purpose — contributing to the vehicle's roadholding/handling and braking for good active safety and driving pleasure, and keeping vehicle occupants comfortable and a ride quality reasonably well isolated from road noise, bumps, vibrations,etc. These goals are generally at odds, so the tuning of suspensions involves finding the right compromise. It is important for the suspension to keep the road wheel in contact with the road surface as much as possible, because all the road or ground forces acting on the vehicle do so through the contact patches of the tires. The suspension also protects the vehicle itself and any cargo or luggage from damage and wear. The design of front and rear suspension of a car may be different.