Electrides intrinsically hold some unique properties arising from the anionic electrons such as the low work function from their loosely bound nature and extended distribution due to their absence of restriction from atomic orbitals. Leveraging these properties, via first-principles calculations, we firstly propose a new nonmagnetic semiconducting electrene ZrCl₂ ([ZrCl₂]²⁺·2e⁻), which is stable and can be easily exfoliated from its experimentally grown parent layered bulk. Moreover, a spontaneous spin splitting of the anionic electrons and consequently a nonmagnetic–magnetic phase transition are revealed in monolayer ZrCl₂ at a critical doping concentration of 5.0 × 10¹⁴ cm⁻². Assisted by the low-energy effective model, constrained random phase approximation simulation, and Anderson's theory, we demonstrate the mechanism of d⁰ magnetism in the doped monolayer ZrCl₂ and confirm the dual localized and extended nature of these magnetic anionic electrons. These results enable electric-field controllable magnetism in electrenes, showing potential for novel spintronic applications.