In a statement, Roma said that the 30-year-old, who scored three goals in 37 appearances in all competitions on loan at the Italian club last season, has signed a deal that would keep him in the Italian capital until the end of June 2023.
Smalling had taken well to life in Rome and earned himself the nickname ‘Smalldini’ following commanding displays in the Roma defence.
“Nothing in life worth having comes easy,” Smalling said.
“My head and my heart has always been in Rome. I am delighted to now be yours. Daje (come on) Roma!”
The deal, which had dragged on for most of the transfer window and reportedly was only registered with barely any time to spare, includes a further five million euros in add-ons according to media reports.
Smalling was signed by Sir Alex Ferguson in 2010 from Fulham, and went on to make 323 appearances for the club, scoring 18 goals.
Roma also announced that they had sold Argentine winger Diego Perotti to Turkish side Fenerbahce on transfer deadline day, ending his five-year spell at the club.
Earlier on Monday, United made their second signing of the window as Brazilian international left-back Alex Telles joined from Porto.
