Abstract: A water sprinkler which includes a hollow sprinkler body, a rotor chamber within the body, a freely rotatable stem extending through the body and being in fluid flow communication with the rotor chamber, a sprinkler head on the open end of the stem for rotation therewith, a rotor within the chamber being freely rotatable about the stem and being capable of limited axial sliding movement relative thereto, a water inlet passage communicating with the interior of the stem and also water inlet ports directing water flow into the chamber to cause rotation of the rotor striker means on the rotor co-operable with rotor impact receiving portions on the stem, arranged so that when water flows through the sprinkler, the rotor rotates at high speed and effects relative slower rotation of the stem and sprinkler head.