Rocker covers are covers that are bolted on over rocker arms in an internal combustion engine. They are called valve covers in the United States, Canada, and in situations where Rocker Arms are not present, such as some Overhead Cam, and most Dual Overhead Cam engines. and rocker boxes in the United Kingdom.

On modern engines without rocker arms they are internationally known as "valve cover" but are sometimes referred to as a "cam cover" or "timing cover" if they also cover the timing gear(s) and belt or chain.

V engines (V6, V8, etc.) usually have two rocker covers, one for each bank of cylinders, while straight engines (I4, I6, etc.) and single-cylinder engines usually have one rocker cover. Very large multi-cylinder engines, such as those used in a ship or in aviation, may have one rocker cover for each cylinder, to make removal and installation more manageable.