An image sensor includes a substrate which includes a first surface and a light-incident second surface facing the first surface, a first semiconductor photoelectric conversion element inside the substrate, an organic photoelectric conversion element on the second surface of the substrate, a first floating diffusion region on the first surface of the substrate, a first transfer transistor having a first end connected to the first semiconductor photoelectric conversion element and a second end connected to the first floating diffusion region, and a second transfer transistor having a first end connected to the organic photoelectric conversion element and a second end connected to the first floating diffusion region. The first semiconductor photoelectric conversion element, the first floating diffusion region, and the first transfer transistor and the second transfer transistor may be in a first pixel region of the substrate.