"Management and staff at the Oberhausen Sea Life Centre were devastated to discover that oracle octopus Paul, who achieved global renown during the recent World Cup, had passed away overnight," the aquarium said in a statement.
"He appears to have passed away peacefully during the night, of natural causes," said Sea Life manager Stefan Porwoll.
"His success made him almost a bigger story than the World Cup itself ... We had all naturally grown very fond of him and he will be sorely missed."
For the prediction, two boxes were lowered into octopus's tank, each containing a mussel and the flags of the two opposing teams. The box whose contents he ate would be declared the winner.
His astonishing ability made him a global media phenomenon. His later predictions were carried live on rolling news channels in Germany.
Paul's body is now in cold storage while the aquarium decides "how best to mark his passing".
It has also been grooming a successor, to be named Paul like his mentor.