Abstract: The present invention relates to a security document having a contactless chip with data masking. The security document comprising a transponder of an electronic module connected to an antenna placed on a given surface of a first part of the document, said transponder serving to remotely communicate with a reader via an electromagnetic coupling, and also comprises a passive masking element of said antenna, which is supported by a second part of the document and can move relative to said first part, said masking element being capable of interfering with the coupling between the transponder and the reader for rendering the reading of the document impossible when said second part is in a predetermined position that corresponds to a closed position of the document.