In rail terminology, a railway turntable or wheelhouse is a device for turning round railway rolling stock, usually locomotives, so that they face the direction they came from. It is especially used in areas where economic considerations or a lack of sufficient space have served to weigh against the construction of a turnaround wye. Railways needed a way to turn steam locomotives around for return journeys, as their controls were often not configured for extended periods of running in reverse; also many locomotives had a lower top speed in reverse. Most diesel locomotives, however, can be operated in either direction, and are considered to have "front ends" and "rear ends". When a diesel locomotive is operated as a single unit, the railway company often prefers, or requires, that it be run "front end" first. When operated as part of a multiple unit locomotive consist, the locomotives can be arranged so that the consist can be operated "front end first" no matter which direction the consist is pointed. Turntables were also used to turn observation cars so that their windowed lounge ends faced toward the rear of the train.

In railroad structures, and rail terminology, a wye or triangular junction is a triangular joining arrangement of three rail lines with a railroad switch at each corner connecting to the incoming lines. A turning wye is a specific case.