A rotary pump comprising a housing (1) defining an annular chamber with inlet and outlet ports (12;11), a flexible annular diaphragm (3) forming one side of the chamber spaced opposite an annular wall of the housing (1), and a partition (13) extending across the chamber. The diaphragm (3) comprises an outer surface which engages the annular wall of the housing (1), and an inner surface opposite the first surface, wherein the outer surface is configured to be pressed progressively against the opposite wall of the housing (1), by a rotating means, to force fluid around the chamber. The rotary pump also comprises a reinforcement ring (4) surrounding the rotating means, and which comprises an embedded portion (30) embedded in an inner portion of a central region of the diaphragm (3), and a support portion (34) having a radially outwardly facing surface (35) which faces and supports the inner surface of the diaphragm (3) adjacent to the reinforcement ring (4) during operation of the rotary pump.