A process for converting a liquid hydrocarbon feedstock into lower molecular weight hydrocarbon compounds in a slurry bed reactor operating at a predetermined temperature and pressure, the process comprising: a. mixing the liquid hydrocarbon feedstock and an excess of hydrogen gas in a mixing zone under predetermined conditions of temperature and hydrogen partial pressure to dissolve a portion of the hydrogen gas in the liquid hydrocarbon feedstock to produce a mixture of hydrogen-enriched liquid hydrocarbon feedstock and undissolved hydrogen gas, wherein the liquid hydrocarbon feedstock has a boiling point above 370°C and wherein the mixing zone is maintained at a pressure level of from 5 bars to 200 bars and at a ratio of the normalized volume of hydrogen to the volume of liquid hydrocarbon of 300 to 3000 normalized liters of hydrogen per liter of liquid hydrocarbon; b. introducing the mixture produced in step (a) into a flashing zone under predetermined conditions to separate undissolved hydrogen gas and light hydrocarbon components from the mixture and recovering a single-phase hydrogen-enriched liquid hydrocarbon feedstock containing a predetermined amount of dissolved hydrogen at the saturation level at the prevailing temperature and pressure, wherein the flashing zone is maintained at suitable operating conditions to maintain the predetermined amount of hydrogen gas in solution in the liquid hydrocarbon; c. introducing the single-phase hydrogen-enriched liquid hydrocarbon feedstock into a reaction zone containing at least one slurry bed reactor with at least one catalyst or catalyst precursor and reacting the single-phase liquid feedstock at a pressure in the range 50-300 kg/cm2, a temperature in the range 350-550°C, a hydrogen feed at rates of up to 5000 standard cubic feet per barrel (SCFB), a liquid recycle-to-feed oil to ratio in the range 1:1 - 1:10, a liquid space velocity in the range 0.2-2.0 volume of feed per hour per volume of reactor (V/h/V) to convert at least a portion of the feedstock into lower boiling point hydrocarbon products, wherein the single-phase hydrogen-enriched liquid hydrocarbon feedstock contains all or at least a substantial portion of the requisite hydrogen for the hydroprocessing reaction and the liquid homogeneous catalyst precursor includes a Mo, W, Ni, Co or Ru metal complex or a precursor, or the support material of the particulate heterogenous catalyst is selected from the group consisting of oxides of iron, coal, activated carbon, alumina, and silica-alumina; d. recovering a reactor effluent comprising the converted hydrocarbon products and unconverted liquid feedstock; a. mixing the liquid hydrocarbon feedstock and an excess of hydrogen gas in a mixing zone under predetermined conditions of temperature and hydrogen partial pressure to dissolve a portion of the hydrogen gas in the liquid hydrocarbon feedstock to produce a mixture of hydrogen-enriched liquid hydrocarbon feedstock and undissolved hydrogen gas, wherein the liquid hydrocarbon feedstock has a boiling point above 370°C and wherein the mixing zone is maintained at a pressure level of from 5 bars to 200 bars and at a ratio of the normalized volume of hydrogen to the volume of liquid hydrocarbon of 300 to 3000 normalized liters of hydrogen per liter of liquid hydrocarbon; b. introducing the mixture produced in step (a) into a flashing zone under predetermined conditions to separate undissolved hydrogen gas and light hydrocarbon components from the mixture and recovering a single-phase hydrogen-enriched liquid hydrocarbon feedstock containing a predetermined amount of dissolved hydrogen at the saturation level at the prevailing temperature and pressure, wherein the flashing zone is maintained at suitable operating conditions to maintain the predetermined amount of hydrogen gas in solution in the liquid hydrocarbon; c. introducing the single-phase hydrogen-enriched liquid hydrocarbon feedstock into a reaction zone containing at least one slurry bed reactor with at least one catalyst or catalyst precursor and reacting the single-phase liquid feedstock at a pressure in the range 50-300 kg/cm2, a temperature in the range 350-550°C, a hydrogen feed at rates of up to 5000 standard cubic feet per barrel (SCFB), a liquid recycle-to-feed oil to ratio in the range 1:1 - 1:10, a liquid space velocity in the range 0.2-2.0 volume of feed per hour per volume of reactor (V/h/V) to convert at least a portion of the feedstock into lower boiling point hydrocarbon products, wherein the single-phase hydrogen-enriched liquid hydrocarbon feedstock contains all or at least a substantial portion of the requisite hydrogen for the hydroprocessing reaction and the liquid homogeneous catalyst precursor includes a Mo, W, Ni, Co or Ru metal complex or a precursor, or the support material of the particulate heterogenous catalyst is selected from the group consisting of oxides of iron, coal, activated carbon, alumina, and silica-alumina; d. recovering a reactor effluent comprising the converted hydrocarbon products and unconverted liquid feedstock;