An inbred maize line, designated 366C, having higher row number and ear length compared to Ia5125, early relative maturity, and common rust resistance conditioned by Rp1, the plants and seeds of inbred maize line 366C and descendants thereof, methods for producing a maize plant produced by crossing the inbred line 366C with itself or with another maize plant, and hybrid maize seeds and plants produced by crossing the inbred line 366C with another maize line or plant.