The present embodiments relate to active thermal control of X-ray tubes. In one embodiment, a system includes an X-ray tube having an electron beam target, a rotary bearing supporting the target in rotation, and a coolant flow passage, at least a portion of the coolant flow passage being disposed in the center of the rotary bearing, and the coolant flow passage is configured to receive a coolant. The system also includes a coolant circulating system coupled to the coolant flow passage and configured to circulate the coolant thorough the coolant flow passage, and a control circuit coupled to the coolant circulating system and the rotary bearing, the control circuit being configured to control heat flow between components of the X-ray tube by regulating extraction of heat from the X-ray tube via the coolant and by regulating a rotation rate of the rotary bearing.