Surfers from Newquay Activity Centre discovered the animal and took videos which showed its massive size.
The police and coastguard were called and cordoned off Fistral Beach.
The 16-metre-long whale had been reported acting strangely around Rowan Head on Tuesday (14 November) night.
It is still uncertain how the whale died. Experts are still determining whether the tide will wash the animal back out or if it will need to be moved manually.
The fin whale is the second largest mammal in the world.
