A multistage pump is a pump in which the fluid flows through two or more impellers fitted in series. Hence, such a pump will have multiple liquid chambers or stages connected in series. Each stage consists of an impeller, a combination of a diffuser, and return guide vanes, all housed within the same stage casing.

These impellers are installed in series and rotate on a single shaft driven by a power source (usually a motor). The design of multistage pumps allows the fluid to flow through the chambers only in a linear fashion.