The 2-metre catfish was discovered floating in a sluice in Goßmannsdorf near Würzburg in the German state of Bavaria on Monday. The man-sized fish had a blue and white football jammed in its massive mouth.
"In 30 years with the water police I have never seen such a thing," officer Reiner Jünger told German news agency DDP, adding that the fish probably mistook the ball for prey.
"Whether the fish allowed himself to get caught up in the recent excitement over the Euro 2008 and went for the ball can't be ascertained," Bavarian police said in a statement on Monday.
Catfish are among the largest freshwater predatory fish. Jünger said the fish generally await their prey on the river floor, but sometimes pop up to snag birds from the surface.