A new residuum full hydroconversion slurry reactor system has been developed that allows the catalyst, unconverted oil and converted oil to circulate in a continuous mixture throughout an entire reactor with no confinement of the mixture. The mixture is partially separated in between the reactors to remove only the converted oil while permitting the unconverted oil and the slurry catalyst to continue on into the next sequential reactor where a portion of the unconverted oil is converted to lower boiling point hydrocarbons, once again creating a mixture of unconverted oil, converted oil, and slurry catalyst. Further hydroprocessing may occur in additional reactors, fully converting the oil. The oil may alternately be partially converted, leaving a highly concentrated catalyst in unconverted oil which can be recycled directly to the first reactor. Fully converted oil is subsequently hydrofinished for the nearly complete removal of hetoroatoms such as sulfur and nitrogen.