A steam car is a light car (automobile) powered by a steam engine.
Steam locomotives, steam engines capable of propelling themselves along either road or rails, developed around one hundred years earlier than internal combustion engine cars although their weight restricted them to agricultural and heavy haulage work on roads. The light car developed contemporaneously with both steam and internal combustion engines, as both engineering and road building matured. As the steam car could use the vast experience of steam engines already developed with the steam railway locomotive, it initially had the advantage. In 1900 the steam car was broadly superior and even managed to hold absolute land speed records. By 1920 the internal combustion engine had progressed to such a point that the steam car was an anachronism.
Few steam cars have been built since the 1920s, although the technology is not implausible and projects intermittently occur to recreate a "modern" steam car with modern levels of convenience, performance and efficiency.
The greatest technical challenges to the steam car have focused on its boiler. This represents much of the total mass of the drivetrain, making the car heavier (an internal-combustion-engined car requires no boiler), and requires careful attention from the driver - although even the cars of 1900 had considerable automation to manage this. The single largest restriction is the need to supply feedwater to the boiler. This must either be carried and frequently replenished, or the car must also be fitted with a condenser, a further weight and inconvenience.
The steam car does have advantages, although most of these are now less important than in its heyday. The engine (excluding the boiler) is smaller and lighter than an internal combustion engine. It is also better suited to the speed and torque characteristics of the axle, thus avoiding the need for the heavy and complex transmission required for an internal combustion engine. The car is also quieter, even without a silencer.