A coaxial liquid pressure regulator includes a housing having an inlet portion and an outlet portion, a substantially tubular valve member slidingly accommodated inside the housing and having a longitudinal axial passage and an upstream end with an inlet edge for the liquid, a valve body fixed inside the inlet portion and defining a seat that interacts with the inlet edge of the valve member and forms therewith a port having a variable width. The inlet portion includes an inlet fitting and a collection chamber directly downstream from the inlet fitting and the valve body includes a cantilever element transversely extending from the inner wall of the collection chamber. First and second deflection elements are arranged between the inlet fitting and the inlet edge, which facilitate flow conveyance toward the port and the longitudinal passage of the valve member.