"After 16 years, it's time to say goodbye," Jones wrote on social media. "I came here as a kid with a dream of playing for Liverpool, and I've been lucky enough to actually live that dream.
"Now it's time for a new challenge and a new chapter for me and my family, and I'm excited for what's ahead. But Liverpool will always have a massive part of me."
A Liverpool native, Jones progressed through the club's academy and made his first-team debut a few weeks before his 18th birthday in January 2019.
A year later, Jones wrote himself into the history books by becoming Liverpool's youngest ever captain when he led the team out in the FA Cup against Shrewsbury Town.
Across eight seasons for Liverpool, Jones made 228 appearances and scored 22 goals across all competitions.
He also has plenty of winners medals in his collection, having won two Premier League titles, one FA Cup, two League Cups, one Community Shield and the 2019 FIFA Club World Cup.
In what turned out to be his final season at Anfield, he made 49 appearances across all competitions, but struggled to tie down a regular starting position in Arne Slot's midfield.
"All at Liverpool FC thank Curtis for his dedication and contribution to the club across the last 16 years, and wish him good luck in the next chapter of his career," the club said in a statement.
Jones was also part of the England team which won the U21 Euros in 2023, being named in the team of the tournament.
He made his senior international debut in 2024, scoring against Greece in the Nations League on his first appearance.
Jones joins his fellow England internationals Djed Spence and John Stones in arriving in Milan this summer, after they moved from Tottenham Hotspur and Manchester City, respectively.