A gas pressure regulator (10) is disclosed, comprising a body (12) fitted with a gas inlet stem (14), at a first end of the body (10), for receiving gas from a gas source at a first pressure, and a gas outlet stem or adaptor (16) at a second end of the body (10), for supplying gas at a desired pressure at the gas outlet stem (16). A pressure adjusting mechanism (18) is provided to enable a user to adjust and set the desired pressure, the pressure adjusting mechanism (18) comprising a movable piston arrangement (20). The gas pressure regulator (10) further comprises gas regulating means (22), to regulate gas flowing out of the gas outlet stem (16) to achieve the desired pressure set by the user. The gas regulating means (22) is securely fitted within the body (12) so as to be located within a gas flow path between the gas inlet stem (14) and the gas outlet stem (16), the gas regulating means (22) comprising an encapsulated valve (24) with a lever (26) that can be actuated by the movable piston arrangement (20) of the pressure adjusting mechanism (18).