Abstract: A quick acceleration fluid coupling comprising: a fluid coupling working chamber defined by an impeller attached to a driving shaft, a runner attached to a driven shaft, and an impeller casing attached to the impeller and surrounding the runner; and a passage for supplying hydraulic oil into the fluid coupling working chamber; wherein the passage includes a control valve operable to be fully opened and closed rapidly, and a bypass passage having an oil control orifice, which bypasses the control valve; thereby the rotational speed of the driven shaft can be changed rapidly from the lowest to the highest or vice versa.