The 25-year-old midfielder becomes the latest Englishman to move to the San Siro, following Djed Spence and John Stones through the door in recent weeks.
Inter are reportedly paying Liverpool 35 million euros for the academy graduate, who joined the Reds as a youngster and went on to make his first-team breakthrough at Anfield.
Jones admitted it was an emotional moment as he brought his Liverpool career to an end.
"After 16 years, it's time to say goodbye," Jones wrote on Instagram.
"I came here as a kid with a dream of playing for Liverpool, and I've been lucky enough to actually live that dream.
"Liverpool will be a massive part of me."
Inter described Jones' arrival as the start of a "new, incredible adventure" for the midfielder, who becomes the sixth Englishman to represent the club.
The Serie A champions have been particularly active in adding English talent, with Spence also signing a contract until 2031 and Stones joining after his Manchester City contract expired.
Jones will now begin a new chapter in Italy as Inter prepare to open their Serie A campaign against Monza on Saturday.
