A display panel may include a first display substrate. The first display substrate may include a base layer defining a display area and a non-display area that is adjacent to the display area, a gate line disposed on the base layer, a first insulating layer disposed on the base layer and covering the gate line, and a test line overlapping the non-display area and disposed on the first insulating layer, the test line being in electric contact with the gate line through a first contact hole defined in the first insulating layer.