4D Theater refers to a custom, multimedia visitor attraction for entertainment and/or education, usually in a theme park, waterpark, museum, heritage center or visitors center. A 4D theater will tell a story using some combination of media such as high-definition video  enhanced by in-theater effects such as props, animatronics, lighting and sound effects, and special 4D theater seats with built-in water sprayers, leg ticklers and transducer speakers (Buttkickers™).

Live actors are sometimes also part of the experience. Well-known examples of 4D theater are Muppetvision 3D (Disney) and Terminator 2:3D (Universal). Other examples include the Revolutionary War Theatre at the Donald W. Reynolds Education Center on George Washington's former estate in Mount Vernon, VA, which includes snow effects to dramatize Washington's army crossing the Delaware, and the Shuttle Launch Experience at Kennedy Space Center in Florida, which uses a one-degree motion base and a panoply of 4D theater effects to simulate the experience of taking off in a space shuttle and orbiting Earth. Even experienced, flown astronauts have endorsed the realism of the 4D theater experience as it plays out in Shuttle Launch Experience.

The term "4D theater" is of course a technical exaggeration to indicate that the experience of 4D theater is in some undefinable realm beyond ordinary human experience in the three-dimensional world, and also that 4D theater surpasses a typical 2D film or video viewing experience and also a typical 3D viewing experience that lacks the 4D theater effects and other extras. The idea of 4D theater is that all the human senses will be involved, and so 4D theaters have seats that vibrate, tickle and spray water, lights that flash, live performers supporting the fiction. All these elements are carefully integrated to work in concert and encourage the visitor to suspend disbelief and enter fully into the 4D theater experience.

Some vendors have begun to eschew the term 4D theater and started to call their products 5D theater instead, in order to be competitive with established 4D theater practices and companies. 4D theater can be seen as the successor to motion simulation theater and many 4D theaters are installed in spaces where the bulky old motion base seats have been removed. 4D theater is dramatic but a fairly mild experience in actual physical terms so that it is family-friendly and most people can enjoy it without physical risk.