Having extended his contract with Manchester United in December which is expected to expire in 2022, Smalling has now joined As Roma on a season-long loan.
"This is the perfect opportunity for me," Smalling said in a statement.
"The chance to experience a new league, with a big team that has got big aspirations is exactly what I needed.
"Hopefully I can hit the ground running. I'm looking forward to joining up with my team-mates."
Roma sporting director Gianluca Petrachi added:
"We are pleased to bring a player like Chris, who has so much experience, to Roma. We are convinced he will help the growth of this squad and all the lads he plays alongside."
Enjoying more first-team opportunities since arriving at Old Trafford, the 29-year-old has seen his game time limited following the arrival of Ole Gunnar Solskjaer.
Aside the arrival of Solskjaer, former Leicester City defender Harry Maguire who joined Manchester United on the eve of the season has made it more difficult for Smalling to cement a place in the match-day squad of the Norwegian trainer.
And to be a first-choice option at the back, Smalling has reportedly agreed personal terms with I Giallorossi to facilitate a temporary move away from the club.
Fallen down the pecking order at the club, one major factor that has seen Smalling set to seek pastures green in Italy is the availability of Maguire, Victor Lindelof, Axel Tuanzebe, Phil Jones and Marcus Rojo.
Smalling will be a replacement for departed Greek centre-half Kostas Manolas who joined Napoli in the summer after Roma missed out on the signings of Liverpool’s Dejan Lovren and Juventus’ Daniele Rugani to fill his left void.
Smalling was recruited from Fulham in 2010 for an undisclosed fee and has gone on to make 200 appearances for Manchester United, winning five major honours.
With Alexis Sanchez sealing a move to Inter Milan on a loan deal this week, Smalling looks set to become the second Manchester United player to join an Italian club on loan.
The versatile defender, who has not featured for Manchester United in the new Premier League season scored just a goal in twenty-four Premier League games for the club last term.
