Disclosed are a light guide (750) and an electronic device including a light guide for coupling ambient light to a light sensor. The light guide (750) that is a structure of light-transmitting material having an elongate shape including a first end (752) for receiving ambient light and a second end (754) for collecting ambient light to transmit to a light sensor. The first end (752) of the light guide has a concave shape and the second end (754) of the light guide also has a concave shape. An electronic device may support the light guide and a light sensor. The concave shape of the second end of the light sensor may disperse light toward the light sensor, rather than tightly focusing the light toward the light sensor. Accordingly, the light sensor may have a sensing area that forms a detection plane so that the detection plane is positioned adjacent to the second end.