Leopold, who captained Hannover throughout the 2025-26 season, arrives without a fee after his deal at the second-division club expired. He made 124 competitive appearances for Hannover across four seasons following his move from SC Freiburg's reserve side in 2022, contributing eight goals and 17 assists.
This season he started in 27 of 28 Bundesliga 2 appearances and contributed three goals and four assists as Hannover narrowly missed promotion on the final day.
Borussia Monchengladbach sporting director Rouven Schröder was emphatic about why the club pursued Leopold.
"He is one who leads the way, who does his job on the pitch with discipline and high intensity, but who is also a good footballer with a pronounced tactical understanding and who made a big step forward in terms of leadership last season as captain of his team," Schröder said. "It was his great wish to play in the Bundesliga — and we are convinced that this step is logical and right for him."
Leopold follows goalkeeper Daniel Batz from Mainz 05 and left-back David Herold from Karlsruher SC as Gladbach's third confirmed external arrival of the summer. A further two signings are expected to complete the initial wave of recruitment: Japanese midfielder Zento Uno from Shimizu S-Pulse and right-back Yukhym Konoplya from Shakhtar Donetsk are both understood to have agreements in place.
Leopold's profile fits a clear Gladbach template under head coach Eugen Polanski — a positionally intelligent central midfielder capable of breaking lines, winning second balls and providing leadership in a team that finished fifth in the Bundesliga last season but lost all three of their Europa League group stage matches.
He was born in Stuttgart to a German-Togolese family, came through the Freiburg academy system from the age of 14 and established himself as one of the 2. Bundesliga's most consistent performers before moving to Gladbach. The free transfer represents strong value for a player his age with established top-level experience.
Hannover, who needed promotion to retain several key players, will now face a significant rebuild of their own following a season that promised more than it delivered.
Leopold arrives in Mönchengladbach ready to begin the next chapter immediately.