Abstract: The invention relates to a flow conditioner for conditioning a fluid flow comprising a pipe having a constriction with a reduced pipe cross-section, at least one ring-shaped element arranged inside the pipe which has an outer diameter which is smaller than the inner diameter of the pipe in the axial region of the pipe in which the at least one ring-shaped element is arranged, and having an areal web whose surface normal is not in parallel with the pipe axis. The invention further relates to a throughflow measurement system for measuring a fluid throughflow through a pipe having a measurement device and a flow conditioner in accordance with the invention arranged upstream of the measurement device.