A display device includes: a display panel; and a window on the display panel, wherein the window includes a glass substrate having a thickness of 20 micrometers (μm) to 100 μm, and the glass substrate contains, on a basis of an entirety of the glass substrate, more than 75 mol % and less than 85 mol % of SiO2, more than 10 mol % and less than 20 mol % of Na2O, and more than 0 mol % and less than 10 mol % of CaO, respectively.