**Gustaf Gründgens (1899-1963)** was a celebrated German actor, director, and theatre director whose career, although primarily linked to the stage, also left an indelible mark on cinema.

His most iconic cinematic role was that of the underworld boss, the ruthless Schränker, in Fritz Lang's expressionist masterpiece, *M - Il mostro di Düsseldorf* (1931). In this film, Gründgens embodied a figure of cold calculation and detached cruelty, which became emblematic of his style.

He excelled at portraying complex characters, often authoritarian, intellectual, and morally ambiguous, with an aura of elegant malevolence. His acting was characterized by an almost surgical precision, impeccable diction, and an intense stage presence, which lent his cinematic roles (though few, such as *Der Rebell* (1932) or *Friedemann Bach* (1941)) an aura of sophisticated cunning and unsettling charm.