The invention concerns a filter element as well as a liquid filter wherein the filter element is axially insertable into the filter housing (10, 11). The filter element (21) effects after mounting the closure of a non-return device for the raw liquid to be filtered with at least one non-return diaphragm (27). The non-return diaphragm (27) is attached to a terminal disk (24) of the filter element (21) in such a way that it effects an axial and/or a radial sealing action of the raw side (32) relative to the clean side (33) in the filter housing (10, 11). On the filter housing (10, 11) a drainage opening (18) for liquid is provided that is closed off by an additional sealing surface (31, 49) of the non-return diaphragm (27) when the filter element (10, 11) is installed.