Laundry washing machine comprising an outer boxlike casing provided with a laundry loading/unloading opening provided on the top wall of said boxlike casing and allowing the access to the revolving drum housed in an axial rotating manner inside a hollow washing tub arranged inside the casing, and a detergent dispenser which is located at the laundry loading/unloading opening and is structured to selectively drop a mixture of detergent and water into the washing tub, wherein said detergent dispenser comprises a substantially basin-shaped container which is provided with at least one detergent compartment shaped to be manually fillable with a given amount of detergent, and a corresponding siphon assembly which communicates with said detergent compartment and is shaped for draining out of the basin-shaped container a liquid-type detergent stored within the detergent compartment when a given amount of fresh water is channeled into the detergent compartment, wherein said siphon assembly comprises two straight sleeves that are inserted one inside the other, at least partly spaced one another, and are arranged inside the detergent compartment, wherein the inner of said straight sleeves extends in pass-through manner across the bottom of the basin-shaped container and protrudes upwards inside the detergent compartment up to a given height, and the outer of said straight sleeves is provided with a closed upper end and extends downwards from slightly above the top of the inner straight sleeve so as to enclose the inner straight sleeve up to a given distance from the bottom of the detergent compartment, wherein said basin-shaped container is provided with a pass-through opening shaped so as to allow the free outflow, out of said basin-shaped container, of a powder-type detergent stored within the detergent compartment when a given amount of fresh water is channeled into said detergent compartment, wherein said detergent dispenser comprises a hand-operated, movable closing member which is attached to the basin-shaped container and is movable between a closing position in which the movable closing member seals up in watertight manner said pass-through opening, and an opening position in which the movable closing member does not close the pass-through opening thus allowing the free outflow of the detergent stored within the detergent compartment through said pass-through opening, characterized in that the movable closing member comprises a plug element, fixed to the basin-shaped container so as to be manually displaceable to and from a closing position in which said plug element closes said pass-through opening, and a sealing gasket, arranged on the plug element so as to abut, when the plug element is arranged in the closing position, against the perimeter of said pass-through opening to seal up said pass-through opening, wherein the plug element comprises a sliding block which is attached in sliding manner to the basin-shaped container so to be manually displaceable between a first and a second working position, and a surface pad which is made of a suitable elastomeric material and is arranged on the sliding block so as to be aligned, when the sliding block is arranged in the first working position, to said pass-through opening to seal up said pass-through opening, wherein the movable closing member comprises a manually-operable element which is connected to the sliding block so to allow the user to manually displace the sliding block between the first and the second working position, wherein said manually-operable element juts out of a lateral wall of the basin-shaped container that faces the center of the laundry loading/unloading opening.