The Serie A champions have paid an initial €30m (£25.7m), rising to €35m (£30m) with add-ons, for the 25-year-old midfielder, who has signed a contract running until 2031, ending a 16-year association with his boyhood club.
Liverpool had rejected a verbal offer of €25m (£21.7m) from Inter in June, valuing their academy graduate at closer to £35m with only a year left on his contract, before a more recent suggestion that a package similar to the £30m Inter Milan paid Tottenham for Djed Spence would get a deal done.
The Reds have also negotiated a 10% sell-on clause as part of the agreement. Inter's interest was not new: the Italian club had proposed a loan with a view to a permanent transfer back in January, an approach Liverpool turned down at the time.
"It's a club that I've wanted to join for a while now so I'm excited," Jones said.
"I'm a Scouse kid who came all the way through [at Liverpool] but I'm at a point now when I want to take the next step and I think this is the perfect club."
Jones made 228 appearances for Liverpool after being given his debut by Jürgen Klopp in 2019, having joined the club's academy at the age of nine. During his time on Merseyside he won two Premier League titles, two Carabao Cups, the FA Cup and the Club World Cup, and was a Champions League runner-up in 2022.
Last season he featured 49 times across all competitions but started only 18 Premier League matches as he struggled for a regular role in Arne Slot's midfield. He becomes the third English player to arrive at Inter this summer, following John Stones and Spence through the door at San Siro, as Cristian Chivu's side continue their push for a title defence after last season's league and cup double.
Jones marked his exit with a lengthy message on Instagram.
"After 16 years, it's time to say goodbye," he wrote. "This club is all I've ever known. I came here as a kid and I'm leaving as a man with a family of my own, which probably puts into perspective just how much of my life I've spent here.
"Liverpool will always be a massive part of me. I came here as a kid with a dream, and I'm leaving having lived it."