A block heater is an electric heater that heats the engine of a car. This allows easier starting in cold temperatures.

Factory installed block heaters are usually inserted into a manufacturing hole in the cylinder block, heating the metal, coolant and oil. After market heaters are often attached to the oil pan so that the engine oil is heated and the viscosity low. In addition to easier starting, block heaters reduce pollution as cold engines have a much higher emission.

Block heaters are often standard equipment for vehicles sold in colder climates. In extremely cold climates, electrical outlets are standard equipment in public parking spots.

An alternative to block heaters is a battery warmer which keeps just the battery warm. This maintains the efficiency of the battery and is cheaper than heating the entire engine block.