Image sensors are provided. The image sensors may include a substrate including first, second, third and fourth regions, a first photoelectric conversion element in the first region, a second photoelectric conversion element in the second region, a third photoelectric conversion element in the third region, a fourth photoelectric conversion element in the fourth region, a first microlens at least partially overlapping both the first and second photoelectric conversion elements, and a second microlens at least partially overlapping both the third and fourth photoelectric conversion elements. The image sensors may also include a floating diffusion region and first, second and third pixel transistors configured to perform different functions from each other. Each of the first, second and third pixel transistors may be disposed in at least one of first, second, third and fourth pixel regions. The first pixel transistor may include multiple first pixel transistors.