The present invention discloses a hydraulic fluid accumulator comprising a housing having an interior subdivided into three chambers, with the first chamber being filled with a gas and separated from the second chamber by a first media separation element, the second chamber being filled with a fluid and separated by a second media separation element from the third chamber that is also filled with a fluid and connected to a hydraulic port. To safeguard an effective separation of media within the hydraulic fluid accumulator and, thus, a significant increase in its functional safety, the present invention arranges for the second media separation element to be embodied by a metal piston delimiting a chamber that can be vented in the housing.