Mutual fidelity is one of the fundamental duties of a married couple (Article 23(2) of the Family and Guardianship Code); there is no doubt that a breach of this duty, i.e. marital infidelity, can have an extremely negative effect on the functioning of the marriage and lead to legal separation or divorce. It is clear, however, that not every case of marital infidelity leads to legal separation or to the dissolution of the marriage by divorce; in particular, it may happen that the marriage relationship is terminated by the death of the betrayed spouse. The question then arises as to whether and, if so, what legal consequences under the law of succession may arise in the legal sphere of the spouse who has committed a breach of marital fidelity. The purpose of this article is to try to answer this question without claiming to be an exhaustive study of the problem outlined. The remarks made here will not, in principle, concern separated spouses since legal separation excludes the legal succession of the deceased spouse (Article 9351 of the Civil Code). A separated spouse could, therefore only inherit from a deceased spouse by way of a will, which is likely to be rather rare.