An improved hydraulic coupler suitable for interconnecting subsea fluid lines is provided with a highly reliable metallic seal between the male and female portions. A C-shaped metallic seal is radially compressed between the female and male coupler bodies, so that axial movement between these bodies does not effect sealing effectiveness. A floating retainer ring housed within the retrievable female body by a fixed retainer ring allows for radial misalignment between the coupling halves. The floating retainer ring thus becomes centered with respect to the male coupling body, while a metallic face seal provides sealing engagement between the floating and fixed retainers. Both axial and radial deviation between the coupling bodies is thus permissible, and the coupling can reliably seal fluid after repeated coupling and uncoupling operations.