A window includes a substrate including a folding portion foldable with respect to a folding axis extending in a first direction. A plurality of groove patterns are defined in the folding portion. The folding portion includes a center portion and an outer portion, and the plurality of groove patterns include a first groove pattern disposed in the center portion and a second groove pattern disposed in the outer portion. The first groove pattern includes a first upper groove pattern and a first lower groove pattern, and the second groove pattern includes a second upper groove pattern and a second lower groove pattern. The first upper groove pattern and the first lower groove pattern partially overlap in the second direction, and the second upper groove pattern and the second lower groove pattern do not overlap in the second direction.