German rap is a subgenre of rap music.

Die Fantastischen Vier (fantastic four) are probably the most prominent German rappers. They were the first German band to appear in MTV Unplugged. Other important crews and rappers include:

Advanced Chemistry, multicultural pioneers from Heidelberg who maintained a political and strictly underground stance. Members include Torch and Toni L, both also started solo careers.
Fuenf Sterne deluxe from Hamburg who focus mainly on fun; though provide innovative beats.
Roedelheim Hartreim Projekt
Ferris MC
Kool Savas
Die Firma
Der Klan

Note that after the United States, Germany is the second-biggest hip hop nation, sales-wise...