"Brian Brobbey fits the profile of RB Leipzig perfectly as a young, very variable and assertive player," said sports director Markus Kroesche.
Despite having had "several offers from other top European clubs", Brobbey has signed with Leipzig until June 2025, Kroesche added.
Brobbey said he is looking forward to working under Leipzig's 33-year-old head coach Julian Nagelsmann.
"Julian Nagelsmann is a young and very good coach from whom I can still learn a lot," said Brobbey.
"I'm really looking forward to joining the team and I would like to do my part to ensure that the club continues to be so successful."