A window member includes a main part including a first side extending in a first direction, a second side extending in a second direction, and a first corner side connecting the first and second sides. The window member further includes a first side part in contact with the first side, a second side part in contact with the second side, and a first corner part connecting the first and second side parts. The first corner part includes a first upper corner part, a first middle corner part, and a first lower corner part. A lower surface of the first middle corner part has a first radius of curvature, a lower surface of the first lower corner part has a second radius of curvature, and the first radius of curvature is greater than the second radius of curvature.