The 24-year-old joins on a permanent transfer worth around €1m, with Everton retaining a 30 per cent sell-on clause, and has signed a three-year contract running until June 2029.
It brings to an end a spell on Merseyside that never fulfilled the promise Everton saw when they signed him from Rangers in January 2022 as one of Scottish football's most highly-rated young full-backs.
Those who worked with him at Everton do not describe a player who failed to deliver, and the British press largely painted him as a talented, promising defender undone by fitness problems and misfortune rather than a lack of quality.
He was well liked in the Everton dressing room and a positive presence around the group, but rarely proved as decisive on the pitch as his profile suggested he could be. Strong in the tackle, a good runner and a reliable crosser of the ball, those attributes alone were not enough to hold down a starting spot in the Premier League — not in this era, at least.
His profile has remained essentially the same since his days at Ibrox, covering for James Tavernier on Rangers' right flank before his move south.
Everton ultimately proved the wrong stage for him, and Torino now represent an opportunity for a fresh start. Sporting director Davide Vagnati moved for Patterson with his eyes open: limited minutes last season, a contract with only a year left to run, and a deal that came together late in the window.
Patterson made just one appearance in all competitions this season under David Moyes, having managed only nine games last term amid a persistent muscle injury, and has found himself behind Merlin Rohl in the right-back pecking order at Goodison Park.
He does, however, arrive with recent international pedigree, having made three appearances for Scotland at this summer's World Cup before Steve Clarke's side exited at the group stage.
Torino's plan is straightforward: either Patterson returns to playing regularly and rediscovers his old sharpness, or the promise attached to his name for years finally goes unfulfilled. The club is offering him precisely that platform — three years to prove whether the drive that once marked him out in Glasgow is still there.