An air/oil separator includes a housing having an inlet for aerated oil or hydraulic fluid and outlets for the separated air and oil or fluid. The housing is generally cylindrical and defines an upper, inlet portion, a center, separator portion and a lower collector portion. The upper, inlet portion of the housing includes a first, tangential inlet passageway which merges with a second, spiral or circular passageway. The spiral or circular passageway communicates with the cyclonic separator portion which may be either cylindrical or frusto-conical. A coaxial outlet in the upper, inlet portion allows separated air to return to the engine or transmission housing while an outlet in the lower, collector portion returns oil or hydraulic fluid to the device.