Rotational molding, also known as rotomolding, is a molding process for creating many kinds of mostly hollow items, typically of plastic.

A heated mold causes the material within to melt and form a puddle at the bottom of the mold cavity. The mold is then slowly rotated (usually around two perpendicular axes) causing the melted material to flow into to the mold and stick to its walls. In order to maintain even thickness throughout the part, the mold continues to rotate during the cooling phase. The process was applied to plastics in the 1940s but in the early years was little used because it was a slow process restricted to a small number of plastics. Over the past two decades, improvements in process control and developments with plastic powders have resulted in a significant increase in usage.