Inter Milan was seeking a transfer fee of €7 million to sell Sommer to the Turkish club, as his contract was set to expire within the next 12 months.
However, Galatasaray decided against signing Sommer due to concerns about his age and instead signed Ugurcan Cakir from Trabzonspor for €27 million.
According to reports, Inter Milan will now allow Sommer to run down the remainder of his contract and leave as a free agent next summer.
The club will use the coming year to identify and sign a new, younger goalkeeper to replace Sommer.