Dispenser (1) for the dosed dispensing of liquid media, with a container (3) for holding a liquid medium (4), a manually actuated pump (5), which is arranged on the container (3) and comprises a flood chamber (6) into which liquid medium (4) flows when the container (3) is turned over, for which purpose the flood chamber (6) is fluidically connected at the inlet end to an outlet opening (7) of the container (3), and a dosing piston (8), which is displaceable by an actuating stroke, is arranged in the flood chamber (6) and expels dosed medium (4), and a media channel (9) extending through the dosing piston (8) is widened at the inlet end as a volumetrically defined cylinder portion (10) into which a plunger piston (11) protruding into the flood chamber (6) engages as a pressure piston in order to expel medium (4) introduced by gravity into the cylinder portion (10) of the dosing piston (8).