The winger arrives having won two Coppa Italias and one Italian Super Cup, as well as the 2020 European Championships with his country Italy.
Chiesa was thought to be out of favour with new manager Thiago Motta and therefore allowed to leave for a cut-price fee, reportedly around £12.5m.
He becomes Liverpool's first summer signing for the 2024/25 season - not counting Giorgi Mamardashvili who was announced earlier in the window but won't join until the summer of 2025.
Upon joining the Reds, Chiesa said: "I'm so happy to be a Liverpool player.
"When Richard Hughes called me and he said, 'Do you want to join Liverpool?' – and the coach called me – I said yes immediately because I know the history of this club, I know what it represents to the fans.
"So, I'm so happy and I can't wait to get started."
The winger enjoyed a good spell in Italy, first debuting for Fiorentina aged 18 before securing a two-year loan move to Juventus in 2020 that became permanent in 2022.
He would suffer an anterior cruciate ligament injury in the middle of the 2022/23 season and face 10 months on the sidelines before returning to action last year, scoring 10 goals in 37 appearances in all competitions.
Chiesa's Liverpool debut could come against Manchester United on Sunday, September 1st.
