Actively cooled heat-dissipation lid for removing excess heat from heat-generating devices attached to printed circuit boards, processor assemblies and other electronic devices, the actively cooled heat-dissipation lid comprising a first plate configured to be placed in thermal communication with a heat-generating device, a raised sidewall to facilitate fastening the actively cooled heat-dissipation lid to the printed circuit board or processor assembly, and thereby defining a device chamber for the heat-generating devices on the printed circuit board to reside. A second raised sidewall extends from the opposite surface of the first plate to join with a second plate in a spaced relation to the first plate, wherein the opposite surface of the first plate, the second raised sidewall and the second plate together define a fluid chamber that is adjacent to the device chamber, the fluid chamber being configured to prevent any cooling fluid flowing therethrough to enter the adjacent device chamber. An inlet conduit in fluid communication with the fluid chamber is configured to admit coolant fluid from a pressurized source to pass into the fluid chamber to absorb heat from the second surface of the first plate in thermal communication with the heat-generating device. An outlet conduit in fluid communication with the fluid chamber is configured to let warmed coolant fluid flow out of the fluid chamber and into a closed loop fluid-cooling system, where the coolant fluid is then re-cooled before being pumped back into the fluid chamber via the inlet conduit.