Provided are a metal oxide-carbon nanomaterial composite, a method of preparing the metal oxide-carbon nanomaterial composite, a catalyst, a method of preparing the catalyst, and a catalyst layer that includes the catalyst and that is used for fuel cell electrodes. The metal oxide-carbon nanomaterial composite includes a metal oxide particle having a specific surface area of 5 square meters per gram (m2/g) or less, and a carbon nanomaterial formed on a surface of the metal oxide particle. The catalyst includes a metal oxide-carbon nanomaterial composite in which a carbon nanomaterial is formed on a metal oxide particle, and an active metal particle formed on a surface of the carbon nanomaterial.