Standing at 6’7”, Lucca joins Sean Dyche’s side as they seek to turn a disappointing Premier League campaign around.
Lucca struggled at Napoli, scoring just one goal in his 16 Serie A games, four have which have been from the first whistle.
Forest have now confirmed that Lucca has joined on an initial loan, paying €1m for the next six months and an option to buy for €40m.
Forest’s Global Head of Football, Edu Gaspar said: “Lorenzo is a player who adds specific qualities to our team, and we are really pleased he has joined us.
“Having played at the top level in different countries, he arrives with a good blend of experience and scope to continue developing as a player.
“Everyone at the Club welcomes Lorenzo, and we are all looking forward to seeing the impact he can have for the rest of the season.”