The present study deals with Gallicisms that are susceptible of becoming "false friends". That is to say, Spanish words of French origin that are formally similar to their French equivalents but present divergences in meaning. These words therefore cause interferences when either one is used. This work is preceded by a theoretical analysis that justifies the validity of the lexicographic proposal. It analyses the different interpretations of the concepts of 'Gallicism' and 'false friends', elaborates the 'state of affairs' and provides a typology sketch that serves as a starting point for later classification. The study culminates in a lexicographic proposal that constitutes an authentic Dictionary of Gallicisms and False Friends by word pairs. To this end, a corpus of Gallicism was established using the «Dictionary of the Spanish Language» (DLE). Once the corpus of Gallicisms had been constituted, they were compared with their French etymons, extracted from the «Petit Robert de la Langue Francaise». This detailed comparison allowed, in a second phase, the selected Gallicisms to be classified into the following categories according to their level of similarity or disparity with their French counterparts: – “Total false friends”: those word pairs that do not share any type of meaning. – “Partial false friends”: those word pairs that share one or several meanings, but not all. Furthermore, three subcategories were created within this category according to the direction in which the interference operates, allowing for a better understanding of the phenomenon. Each of these four categories has either convergence or divergence sections, according to each individual case. Finally, an Observation Section has been included, reserved for the historical and contrasting explanations that have been considered pertinent. Also, the contributions of the most important historical dictionaries, both French and Spanish, as well as encyclopedic and specialized lexicography, have been taken into account. This dictionary can be very useful for both Spanish speakers learning French and for French speakers learning Spanish, as well as for translators in one direction or the other.