Abstract: The invention relates to a connection device for earthing an electrical apparatus or putting it at a reference potential. It is inserted between a first electrically conductive part belonging to said electrical apparatus and a second part belonging to a support structure on which said electrical apparatus is mounted and which may be at least partly electrically insulating. It is characterized in that it comprises a first automatic connection area for automatically creating electrical contact with said first part, and a second automatic connection area for automatically creating electrical contact with an electrical conductor that is earthed or connected to a reference potential, when said electrical apparatus is mounted on said support structure. The electrical apparatus is thus automatically earthed or connected to a reference potential when it is mounted on said support structure via said connection device and said electrical conductor, specifically without any tools, screws or any other fastening member.