Abstract Solution‐processed quantum dot (QD) based blue emitters are of paramount importance in the field of optoelectronics. Despite large research efforts, examples of efficient deep blue/near UV‐emitting QDs remain rare due to lack of luminescent wide band gap materials and high defect densities in the existing ones. Here, we introduce a novel type of QDs based on heavy metal free gallium sulfide (Ga 2 S 3 ) and their core/shell heterostructures Ga 2 S 3 /ZnS as well as Ga 2 S 3 /ZnS/Al 2 O 3 . The photoluminescence (PL) properties of core Ga 2 S 3 QDs exhibit various decay pathways due to intrinsic defects, resulting in a broad overall PL spectrum. We show that the overgrowth of the Ga 2 S 3 core QDs with a ZnS shell results in the suppression of the intrinsic defect‐mediated states leading to efficient deep‐blue emission at 400 nm. Passivation of the core/shell structure with amorphous alumina yields a further enhancement of the PL quantum yield approaching 50 % and leads to an excellent optical and colloidal stability. Finally, we develop a strategy for the aqueous phase transfer of the obtained QDs retaining 80 % of the initial fluorescence intensity.