Method for determining a wind speed in the plane of a rotor of a wind turbine, characterized in that the following steps are implemented: a. constructing a wind turbine model that links the rotational speed of said rotor of said wind turbine, the tilt angle of the blades of said wind turbine, and the power generated by a conversion machine of the wind turbine to the wind speed in the plane of the rotor of said wind turbine, by way of the following steps: i. simultaneously measuring (LID, MES1) the wind speed in the plane of the rotor of said wind turbine along with the rotational speed of said rotor, the tilt angle of the blades and the power generated by said conversion machine of said wind turbine; ii. classifying said simultaneous measurements of the wind speed in the plane of the rotor of said wind turbine along with the rotational speed of said rotor, the tilt angle of the blades and the power generated by said conversion machine of said wind turbine into at least two classes of operating conditions of the wind turbine; iii. for each class, determining a regression between the measurements of the wind speed in the plane of the rotor of said wind turbine along with the rotational speed of said rotor, the tilt angle of the blades and the power generated by said conversion machine of said wind turbine using a basic function decomposition method, and using a method for establishing a relationship between these basic functions and the wind speed in the plane of the rotor, preferably by way of a Gaussian process regression method and using a least squares regression method; iv. constructing said wind turbine model by way of said regressions determined for each class; b. measuring, in real time (tpr), the rotational speed of said rotor, the tilt angle of the blades and the power generated by said conversion machine of said wind turbine; and c. determining, in real time (tpr), the wind speed v in the plane of said rotor of said wind turbine by way of said real-time measurements of the rotational speed of said rotor, of the tilt angle of the blades and of the power generated by said conversion machine of said wind turbine, and said wind turbine model. a. constructing a wind turbine model that links the rotational speed of said rotor of said wind turbine, the tilt angle of the blades of said wind turbine, and the power generated by a conversion machine of the wind turbine to the wind speed in the plane of the rotor of said wind turbine, by way of the following steps: i. simultaneously measuring (LID, MES1) the wind speed in the plane of the rotor of said wind turbine along with the rotational speed of said rotor, the tilt angle of the blades and the power generated by said conversion machine of said wind turbine; ii. classifying said simultaneous measurements of the wind speed in the plane of the rotor of said wind turbine along with the rotational speed of said rotor, the tilt angle of the blades and the power generated by said conversion machine of said wind turbine into at least two classes of operating conditions of the wind turbine; iii. for each class, determining a regression between the measurements of the wind speed in the plane of the rotor of said wind turbine along with the rotational speed of said rotor, the tilt angle of the blades and the power generated by said conversion machine of said wind turbine using a basic function decomposition method, and using a method for establishing a relationship between these basic functions and the wind speed in the plane of the rotor, preferably by way of a Gaussian process regression method and using a least squares regression method; iv. constructing said wind turbine model by way of said regressions determined for each class; i. simultaneously measuring (LID, MES1) the wind speed in the plane of the rotor of said wind turbine along with the rotational speed of said rotor, the tilt angle of the blades and the power generated by said conversion machine of said wind turbine; ii. classifying said simultaneous measurements of the wind speed in the plane of the rotor of said wind turbine along with the rotational speed of said rotor, the tilt angle of the blades and the power generated by said conversion machine of said wind turbine into at least two classes of operating conditions of the wind turbine; iii. for each class, determining a regression between the measurements of the wind speed in the plane of the rotor of said wind turbine along with the rotational speed of said rotor, the tilt angle of the blades and the power generated by said conversion machine of said wind turbine using a basic function decomposition method, and using a method for establishing a relationship between these basic functions and the wind speed in the plane of the rotor, preferably by way of a Gaussian process regression method and using a least squares regression method; iv. constructing said wind turbine model by way of said regressions determined for each class; b. measuring, in real time (tpr), the rotational speed of said rotor, the tilt angle of the blades and the power generated by said conversion machine of said wind turbine; and c. determining, in real time (tpr), the wind speed v in the plane of said rotor of said wind turbine by way of said real-time measurements of the rotational speed of said rotor, of the tilt angle of the blades and of the power generated by said conversion machine of said wind turbine, and said wind turbine model.