A revolving door is a type of door that, as its name suggests, revolves in its frame.

Most kinds of doors are bolted to the wall and are on hinges. They open only one way, for a theoretical maximum of 180 degrees rotation. Sometimes hinge-doors can open both ways in their frames, for a theoretical maximum of 360 degrees rotation. A revolving door, however, has a theoretical rotation maximum of infinity, as it is set on a rotating shaft.

Around the shaft are several doors that are bolted to it and incapable of independent movement. The usual number of doors on a revolving door is four, although the number may be higher or lower. The doors may be electric (in which case there is a motor at the base of the shaft) or manual, in which case the doors have handle bars on them. When you push on the handlebar of the door in front of you, the entire shaft will rotate around.

Often there is a partial wall around the circumference of the revolving door with only openings sized to match an individual section of the revolving door. In this configuration, the revolving door prevents a direct path between the interior and exterior. This can be used as a partial airlock to minimize heat loss from the building. This can also be used as a security measure to allow only a single person through the revolving door at a time. This is in contrast to a normal door which suffers from easy "tailgating" by a second person when the door is opened for the authorized person.

Revolving door, used metaphorically, also refers to an arrangement between a government regulating agency and an industry whereby people move between the two groups frequently and easily, conjuring the image of a revolving door between the two, with connotations of overly close relationships and possibilities for abuse.