Provided is an image sensor including a first substrate including a first surface to which light is incident and a second surface opposite the first surface, a second substrate facing the second surface of the first substrate, a wiring layer between the first substrate and the second substrate and including an insulating layer and a conductive structure in the insulating layer, a first floating diffusion region provided in the first substrate, a first through electrode penetrating through the second substrate and electrically connected to the first floating diffusion region through the conductive structure, a second floating diffusion region provided in the second substrate, and a landing pad arranged on a bottom surface of the second substrate and electrically connected to the second floating diffusion region, wherein a bottom surface of the first through electrode may be in contact with the landing pad.