Frigate captain Walter Biot was found guilty by the Court of Assizes in Rome of espionage and bribery after being caught handing over secret documents to Russian embassy officials in a Rome shopping centre in March 2021.
The prosecution had asked for him to be given 18 years.
This was the second sentence handed down to the father of four from Pomezia outside Rome after he was found guilty by a military court and sentenced to 30 years in jail in March 2023.
Italy expelled two Russian embassy officials in 2021 in relation to the case.
ANSA