North Yorkshire Police issued an appeal earlier today to find Mr Gray after he left his home in York in a green Vauxhall Astra.
The sad discovery was made this afternoon.
A force spokesman said: "Officers searching for the 78 year old missing man from York, have sadly discovered a body in the River Ouse.
"The family of the man have been informed and are being supported by officers.
"We ask that the privacy of the family is respected at this extremely difficult time."