A geared steam locomotive is a type of steam locomotive which uses gearing, usually reduction gearing, in the drivetrain, as opposed to the common directly driven design.
This gearing is part of the machinery within the locomotive and should not be confused with the pinion that propels a rack locomotive along the rack between the rails. The geared steam locomotives that have been built have been for conventional track, relying on the adhesion between wheels and rail.
Unlike conventional steam locomotives, they are not classified by their wheel arrangement. Instead, they are classified by their model and the number of trucks they have.