An undersea hydraulic coupling with a hollow metal o-ring seal for sealing between the male and female members is disclosed. The hollow metal o-ring seal is held captive between an internal shoulder and a retainer insertable into the internal bore of the female member. The retainer may be slidable to compress the metal o-ring seal axially. The metal o-ring seal also may be pressure-energized to expand the seal cavity in response to fluid pressure in the coupling.
