A hydraulic accumulator, in particular in the form of a piston accumulator, has an accumulator housing (10) and a separating element (20) arranged in the housing. The separating element is in the form of a piston, which separates a fluid side (22) from a gas side (24). At least the gas side (24) can be inspected, at least in part, by at least one sight glass (34, 36) that is fixed in the accumulator housing (10).