The 18-year-old has represented Serbia at youth level and helped his country reach the semi-finals of last summer’s European Under-19 Championship.
A central or left midfielder, Pantic played for Partizan in last season’s Europa League, and is set to immediately join Dutch side Vitesse Arnhem on loan for the forthcoming campaign.
Pantic said: “I am very happy to sign for Chelsea, the champions of the English Premier League, and I hope I can show my value at Vitesse in the coming season. I am honoured at the faith both clubs have shown in me.”
Pantic becomes the fourth Chelsea player to link up with Vitesse ahead of the 2015/16 season.
English duo Lewis Baker and Izzy Brown, as well as Brazilian Nathan, who signed for Chelsea just last month, have already made the temporary switch to the Eredivisie.