Hydraulic steering device for boats, small vessels or the like, comprising: a hydraulic pump coupled to a drive motor to feed a drive fluid alternately according to two flow directions; at least one hydraulic actuator cylinder connected to the delivery and return of said pump; a fluid flow distributor switching the connection of the delivery and intake of said pump alternatively to one of two inlets / outlets of the cylinder communicating with one of the two chambers of said cylinder; said actuator cylinder being mechanically articulated to a direction variation member by means of a rod which can be displaced relative to the cylinder, which steering variation member determines the direction change by modifying its orientation relative to an axis of said boat, small vessel or the like, preferably to a longitudinal axis; the modification of the orientation of the said direction variation member being implemented by said actuator cylinder as a function of the hydraulic fluid supply to said cylinder caused by the actuation of the pump; and wherein said motor has inputs for a power signal for the operation of said pump to supply the fluid flow according to one of the two provided directions of flow, wherein said cylinder, said pump, said distributor / manifold and said motor are attached together to form an operating unit integrated in a single body, wherein the pump is provided with an integrated tank (26, 27) for the supply fluid of the cylinder, wherein the tank (26, 27) comprises an oil pressure compensation chamber, which chamber is sealed off from the oil containment compartment by means of a movable wall, or a membrane and which chamber is filled with a compressible fluid, characterized in that the chamber is made as a recess in a cap for closing and sealing the tank, said membrane being provided in the form of a sealing gasket between said cap and said tank (26, 27) or integrated with said sealing gasket. a hydraulic pump coupled to a drive motor to feed a drive fluid alternately according to two flow directions; at least one hydraulic actuator cylinder connected to the delivery and return of said pump; a fluid flow distributor switching the connection of the delivery and intake of said pump alternatively to one of two inlets / outlets of the cylinder communicating with one of the two chambers of said cylinder; said actuator cylinder being mechanically articulated to a direction variation member by means of a rod which can be displaced relative to the cylinder, which steering variation member determines the direction change by modifying its orientation relative to an axis of said boat, small vessel or the like, preferably to a longitudinal axis; the modification of the orientation of the said direction variation member being implemented by said actuator cylinder as a function of the hydraulic fluid supply to said cylinder caused by the actuation of the pump; and wherein said motor has inputs for a power signal for the operation of said pump to supply the fluid flow according to one of the two provided directions of flow, wherein said cylinder, said pump, said distributor / manifold and said motor are attached together to form an operating unit integrated in a single body, wherein the pump is provided with an integrated tank (26, 27) for the supply fluid of the cylinder, wherein the tank (26, 27) comprises an oil pressure compensation chamber, which chamber is sealed off from the oil containment compartment by means of a movable wall, or a membrane and which chamber is filled with a compressible fluid, characterized in that the chamber is made as a recess in a cap for closing and sealing the tank, said membrane being provided in the form of a sealing gasket between said cap and said tank (26, 27) or integrated with said sealing gasket.