A liquid filter (10) with a built-in pressure regulator (11) for fuel is proposed, wherein the pressure regulator (11) with its diaphragm (41) is built on the housing (12) on a component (18) on the front with at least one connection (19). The disk-shaped diaphragm (41) has a single clamping site (39) on its external circumference and a centrally arranged movable closure closure member (42). The diaphragm (41) is acted upon by pressure in a pressure chamber (45) connected with the clean side against the force of a spring (49) in a gas-filled spring chamber (48). The integration of the pressure regulator (11) in the housing (12) permits a simple, compact, cost-effective construction of the liquid filter (10), through whose valve (44) in the pressure regulator (11) only cleaned fuel flows and which is insensitive to backpressure in the tank connection (17).