A transparent display panel includes a transparent display structure and a light transmittance adjusting structure. The transparent display structure includes a display region and a transmittance region. The light transmittance adjusting structure is located over or under the transparent display structure. The light transmittance adjusting structure includes a volume changeable material of which a volume is changed in response to intensity of incident light or a photochromic material of which a coloring degree is changed in response to the intensity of incident light. The transparent display panel effectively improves quality of an image displayed on the transparent display panel by maintaining or adjusting a contrast ratio of the image according to the intensity of the incident light.