A liquid filter, in particular for the lubricating oil of an internal combustion engine, having a housing with an inlet and an outlet formed from a housing pot having a substantially downwardly open filter element installation opening and a screw-on cover that closes the installation opening, and a filter element arranged in the housing, sealingly separating the inlet from the outlet. The screw-on cover has a drain for residual liquid present in the housing with a round drain opening arranged in the central axis of the housing. A device for opening and closing the drain opening is arranged in the area of the drain and connected to an end disk of the filter element so that it moves relative to the drain opening and opens the drain when the cover is unscrewed.