<p>Extensive studies on the impact of bismuth incorporation into the (Ga,Mn)As prototype dilute ferromagnetic semiconductor (DFS) on its structural, magnetic, and magnetotransport properties are summarized in this review. Thin epitaxial layers of the quaternary (Ga,Mn)(Bi,As) compound, containing up to 1% Bi and 6% Mn atoms, and the reference ternary (Ga,Mn)As compound, have been grown under either a compressive or tensile biaxial misfit strain by the low-temperature molecular-beam epitaxy technique with precisely optimized growth conditions. High-resolution x-ray diffraction measurements and transmission electron microscopy imaging of cross-sections across the sample interfaces have evidenced high structural perfection of the DFS layers and sharp interfaces with the substrate. An addition of bismuth into the layers causes a small decrease in their ferromagnetic Curie temperature and a distinct increase in the coercive fields, as revealed by the superconducting quantum interference device magnetometry investigations, which also demonstrate a strong effect of biaxial misfit strain in the layers on their crystalline magnetic anisotropy. Most of all, the incorporation of a small atomic fraction of heavy Bi atoms, substituting As atoms in the layer, predominantly enhances the spin–orbit coupling strength in its valence band, considerably affecting the electromagnetic properties of the layers. Investigations of magnetotransport properties of the DFS layers performed on micro-Hall bars prepared from the layers using electron-beam lithography patterning and chemical etching, reveal significantly enhanced magnitudes of magnetoresistance, anomalous and planar Hall effects, and the spin–orbit torque effect as a result of Bi addition to the layers. The last of these is of special interest for application to next-generation non-volatile data storage and logic spintronic devices, utilizing electrically controlled magnetization reversal.</p>