A method controls the rotational speed of a wind turbine having a tower, a nacelle mounted on the tower and a drive train which includes a rotor having at least one rotor blade. The rotor is rotatably mounted about a rotor axis in the nacelle. The drive train further includes a generator configured to be driven by the rotor. In a nacelle-fixed reference system, the rotational speed (ωG*) of a component of the drive train which rotates with the rotor in correspondence to a transmission ratio (Ue) is measured. A movement of the nacelle relative to the ground is measured and the rotational speed is controlled to a rotational speed setpoint with a speed controller which outputs a generator torque (MG) and/or a blade pitch angle (θ). The measured rotational speed (ωG*) is converted into a corrected rotational speed (ωGC) which corresponds to the rotational speed of the rotor in a ground-fixed reference system multiplied by the transmission ratio (Ue). The corrected rotational speed (ωGC) is used as the input quantity for the speed controller.