A hydraulic servomotor control assembly is disclosed, for example a hydraulic servomotor control assembly which supplies the pressurized oil as operating fluid to a hydraulic motor 1, and which controls the volume of the pressurized fluid by means of a servo valve 2. In hydraulic servomotors of the prior art, the hydraulic motor and the tachogenerator or rotational speed sensor device for detecting the rotation, are two separate entities, so that the servomotor must be quite large, and it is difficult to find ways to make it any smaller. In contrast to such prior art, the hydraulic servomotor control assembly according to this invention is distinguished by the fact that a hydraulic motor 1 and a rotational speed detector device (13, 17, 20) are shaft coupled and integral with each other, so that the resulting assembly is both compact and stable.