The Spanish giants needed extra-time to see off the spirited Kashima Antlers 4-2 in Yokohama.
Normal time finished 2-2, with Kashima's pace making a mockery of Real's much-vaunted defence.
However, Ronaldo took over in extra time as he struck twice to take the game away from the Japanese.
But even at 3-2, Kashima responded by rattling the crossbar through Yuma Suzuki. It needed Ronaldo to finally resolve things and he obliged, intercepting a Toni Kroos shot and slotting home himself to bring the trophy back to the Bernabeu.
The hat-trick capped an amazing 2016 for the Portuguese, who has won the Champions League, European Championship and Ballon d'Or.