Posting on Chinese social media site WeChat, the Shanghai government said the park was barring people from entering and those inside could only leave once they had returned a negative test result.
It added that anyone who has visited the park since Thursday must provide three negative test results over three consecutive days.
No date has been given for when the park will reopen. Shanghai Disney said tickets will be valid for six months and refunds will be given.
The snap closure comes just two days after the park began operating at a reduced capacity to comply with Covid measures.
It's not the first time the park has unexpectedly shut. Last November, 30,000 people were trapped inside after authorities ordered everyone to be tested as part of contact tracing.
Surely nothing can possibly go wrong with this policy! Though I, for one, am at least slightly tickled by the thought of a group of people indefinitely trapped at Disney forming their own new society from the inside.