Abstract: An improved releasable coupling device for a tube is disclosed. The coupling device comprises a fitting having a bore therein and an opening into the bore through which the tube is to be inserted, a retaining ring disposed in the opening and having a plurality of axially extending inwardly biased fingers, and an unlocking collar positioned inside of the retaining ring in the opening. The inwardly biased fingers of the retaining ring each have a gripping portion adapted to engage the tube when the tube is inserted into the fitting towards the bore so that the tube is restrained against axial movement out of the fitting. The unlocking collar is axially movable relative to the retaining ring for direct engagement with the fingers upon axial movement towards the fingers to force the fingers radially outward to cause disengagement of the gripping portions from the tube.