The present invention provides a water dispersible carbon fiber, which is excellent in terms of convergence properties and dispersibility. The carbon fiber is formed by convergence of a plurality of single fibers and is (1) a water dispersible carbon fiber, wherein the surface oxygen concentration (O/C) of each of the single fibers is 0.03 or more and less than 0.12 as measured by X-ray photoelectron spectroscopy (ESCA) and a sizing agent containing a surfactant as a major component has adhered to the single fibers, such carbon fiber forming a first contact angle with water of 75° or less as measured by the Wilhelmy method; (2) a water dispersible carbon fiber, wherein the surface oxygen concentration (O/C) is 0.12 or more and less than 0.20 and a sizing agent containing a surfactant as a major component has adhered to the single fibers, such carbon fiber forming a first contact angle with water of 65° or less as measured by the Wilhelmy method; or (3) a water dispersible carbon fiber, wherein the surface oxygen concentration (O/C) is 0.20 or more and 0.30 or less and a sizing agent containing a surfactant as a major component has adhered to the single fibers, such carbon fiber forming a first contact angle with water of 55° or less as measured by the Wilhelmy method.