A mass email says that Southgate has accrued substantial wealth using a crypto trading platform.
It even says the 51-year-old went on American TV host Ellen DeGeneres' show to talk about his success.
A spokesman for Southgate said: "The details about Mr Southgate in this story are completely untrue.
"His name has been used without permission. As such, his management team are taking legal advice on the matter."
England manager Gareth Southgate signed a new contract in November to keep him in the role until December 2024.