Optogenetic techniques provide genetically targeted, spatially and temporally precise approaches to correlate cellular activities and physiological outcomes. In the nervous system, G-protein-coupled receptors (GPCRs) have essential neuromodulatory functions through binding extracellular ligands to induce intracellular signaling cascades. In this work, we develop and validate a new optogenetic tool that disrupt Gα signaling through membrane recruitment of a minimal Regulator of G-protein signaling (RGS) domain. This approach, hoto-nduced odulation of α protein - nhibition of Gα (PiGM-Iq), exhibited potent and selective inhibition of Gα signaling. We alter the behavior of and with outcomes consistent with GPCR-Gα disruption. PiGM-Iq also changes axon guidance in culture dorsal root ganglia neurons in response to serotonin. PiGM-Iq activation leads to developmental deficits in zebrafish embryos and larvae resulting in altered neuronal wiring and behavior. By altering the choice of minimal RGS domain, we also show that this approach is amenable to Gα signaling.