A ship elevator is a structure for lifting ships from one level of a waterway to another. It is an alternative to a lock: instead of a simple chamber which fills or empties to match the level it opens onto, a ship elevator holds a moving platform or lifting device which physically raises or lowers the ship.

A moving mechanical support changes the ship's elevation. The ship is physically raised or lowered rather than merely floating within a fixed chamber whose water level changes.

The lock serves a comparable level-transition purpose through a gated water chamber. The means of changing level distinguishes the two structures.