A leaf spring is a simple form of spring commonly used for suspension in wheeled vehicles. Originally called a laminated spring or carriage, and sometimes referred to as a semi-elliptical spring or carriage spring, it is one of the oldest forms of spring, dating back to medieval times. A leaf spring takes the form of a thin arc-shaped spring steel length of rectangular section. In the most common configuration, the center of the arch provides the location for the shaft, while attachment holes are provided at each end to secure to the vehicle body. For very heavy vehicles, a leaf spring can be made from several sheets stacked on top of each other in several layers, often with progressively shorter leaves. Leaf springs can serve to locate and to a certain extent cushion as well as dock functions. While the friction between sheets provides a damping action, it is not well controlled and results in a stretch in the movement of the suspension. For this reason some manufacturers have used mono leaf springs.

A leaf spring can be fixed directly to the frame at both ends or fixed directly at one end, generally the front, with the other end attached through a shackle, a short swing arm. The shackle takes the tendency of the reed spring to elongate when compressed and therefore makes the elasticity softer. Some springs ended at a concave end, called an end of the spoon (rarely used now), to carry a rotating member. Moon springs are a basic form of suspension made of steel layers of different sizes sandwiched one over the other. Most of the leaf spring configurations are formed in an elliptical shape through the use of spring steel having properties that allow it to flex as pressure is added at each end, but returning to its original position through a Cushioning process. The steel is generally cut into rectangular sections and then once joined by metal clips at each end and a large bolt through the center of the sheets. It is then mounted on the vehicle axle with large U-bolts, securing the suspension in place.