An etchant includes: 5 to 20 wt % of persulfate, 1 to 10 wt % of at least one compound of an inorganic acid, an inorganic acid salt, or a mixture thereof, 0.3 to 5 wt % of a cyclic amine compound, 1 to 10 wt % of at least one compound of an organic acid, an organic acid salt, or a mixture thereof, 0.1 to 5 wt % of p-toluenesulfonic acid, and water, based on the total weight of the etchant. A copper-titanium etchant further includes 0.01 to 2 wt % of a fluoride-containing compound. A method of forming a display device using the etchant, and a display device, are also disclosed.