The concept of poly-quasi-eutectic solvents (PQESs) has been proposed in this study. A class of PQESs composed of polymers, namely polyethylene glycol (PEG), poly(ethylene glycol)-block-poly(propylene glycol)-block poly(ethylene glycol) (P123), poly(propylene glycol) bis(2-aminopropyl ether) (PPG-NH₂), and poly(ethylene glycol) dimethyl ether (DMPEG), and hydrogen bonding donors (HBDs, including carboxylic acids and amides) were prepared, which could be used for dissolving metal oxides. The PQESs were formed by simply mixing the selected polymers and HBDs. The PEG-based PQESs have excellent physiochemical properties, including negligible volatility, low viscosity, intrinsic conductivity, and wide electrochemical windows. Moreover, they were shown to be good solvents for metal oxides, which have potential applications in industrial metallurgical processes.