<p>Copper and its alloys are widely used in aerospace, electronics, energy, and advanced manufacturing because of their excellent electrical and thermal conductivity combined with favorable mechanical properties. However, when exposed to elevated temperatures, these materials are highly susceptible to oxidation, which degrades surface integrity, reduces service reliability, and limits their application in demanding environments. Although substantial progress has been made in recent decades, a systematic and up-to-date review dedicated to the high-temperature oxidation of copper alloys remains lacking. This review summarizes the oxidation behavior of pure Cu and representative Cu-based alloy systems, including Cu–Al, Cu–Ni, Cu–Cr, Cu–Zn, Cu–Be, Cu–Sn, and Cu–Si alloys, with emphasis on oxidation kinetics, oxide-scale structures, and the roles of temperature, oxygen partial pressure, composition, and microstructure. The review further discusses major protection strategies, including alloying design, coating technologies, annealing-induced pre-oxidation, and microstructural regulation. Recent mechanistic advances are also highlighted, such as cross-scale oxide growth, surface homogenization induced by elemental diffusion and consumption, and the construction of atomic-scale protective scales. By integrating classical oxidation theory with recent experimental progress, this review clarifies the governing factors for oxidation resistance in Cu-based alloys and provides perspectives for the design of next-generation copper alloys capable of service under increasingly severe high-temperature conditions.</p>