The Theatrium was launched to mark the reopening of the renovated Hessisches Staatstheater Wiesbaden in 1977. With bratwurst, beer and artistic interludes, the citizens of Wiesbaden were given the opportunity to bid for props and costumes from the Hessian State Theater's collection.

The festival around the Staatstheater, on the Bowling Green and on Wilhelmstraße soon developed into a much-attended event. This is why, in addition to the name Theatrium, the name "Wilhelmstraßenfest" also became established for this major event.

With around 250,000 visitors on average, the Theatrium is one of Wiesbaden's most important festivals.