Abstract: A fluid separator and particularly a fluid separator for use in a shock absorber is disclosed. A monotube shock absorber with such fluid separator includes a pressure tube having a generally cylindrical inner surface bounded by a closed end and an open end that defines a chamber, and a piston/valve located within the chamber and defining within the chamber a first fluid cavity and a second fluid cavity. A fluid separator is located within the chamber between the piston/valve and the closed end, including a generally circular ring having a radially outer portion mounted and sealing about a circumference of the inner surface in a generally fixed relationship and a radially inner portion. The fluid separator includes an elastomeric portion having a flexible membrane mounted to and spanning an area within the radially inner portion of the ring to thereby define a gas chamber between the fluid separator and the closed end.