The Italy international's previous deal ran until 2028. His new contract includes a salary rise from around €3 million per season to approximately €4 million, reflecting his importance to the squad under head coach Luciano Spalletti.
CEO Damien Comolli paid tribute to Locatelli's commitment since his arrival from Sassuolo in 2021.
"We all remember when Manuel, upon his arrival in 2021, spoke with great emotion about how he had always been a Juventus supporter.
"His contract extension therefore represents the natural continuation of the development of his leadership on the pitch, of his strong Juventus spirit, in complete harmony with the club's values and ambitions."
Locatelli, 28, has made 224 appearances for Juventus across all competitions, scoring nine goals and providing 17 assists. He has scored three times and provided two assists in 44 appearances this season, wearing the captain's armband throughout.
He joined the club in a €37.5 million deal from Sassuolo, initially on loan before the transfer was made permanent.
The renewal follows new deals for Kenan Yildiz, Weston McKennie and Spalletti himself in recent weeks. Attention now turns to the future of Dušan Vlahović, whose contract expires this summer and remains unresolved.