Abstract: A pressure vessel for containing a fluid at elevated pressure features an unstressed corrugated metallic liner forming part of a hermetic seal. The liner has corrugations extending parallel to a first direction to accommodate deformation in a second direction perpendicular to the first direction. Around the liner is a filler layer of elastic material forming a contiguous layer adjacent to the external surface of the liner and filling the corrugations. An external primary load-bearing container has at least one wall made of fiber-reinforced composite material adjacent to the filler layer. The shape of the primary container, the reinforcing directions of the fiber-reinforced composite material, and the mechanical properties of the filler layer are configured such that, under a given change in the pressure of the contained fluid, a strain caused in the liner parallel to the first direction is at least one order of magnitude less than a corresponding strain in the second direction.