With an introductory brief presentation of the general features of the development of inheritance law and will as a presupposition of legacies, the main part deals with and analyzes the notions, forms, divisions and functions of legacies and fideicommissa in Roman law. Namely, in the inheritance law, one differs on the one hand the appointment of the heir by will, whereby the testator appoints a universal successor who will acquire all or part (if there are more heirs) of his rights and obligations after his death, and on the other hand the appointment of the legatee, which leads to singular succession, at the expense of the inheritance, but no obligations are transferred to him. The precondition for setting the legacy was originally a will, which was exclusively valid for the basic form of Roman legacies - legatum, while only later, in imperial times, developed another form of legacy - fideicommissa, which could be addressed to the intestate successor as well. The main difference between them was that the legacy was a formal unilateral declaration of will that the recipient of the legacy had to act on, while the fideicommisum (trust) was an informal request by the testator to the recipient of some part of inheritance to do something for the fideicommisarius. Taking into account the fact that legacies are still present in our positive law, the study of Roman legal sources is followed by the analysis of the basic features and the regulation of legacies in contemporary Croatian law of inheritance, taking also into account the relevant judicial practice. It is pointed out to what extent the institute of legacy in contemporary Croatian law owes its development to the Roman legal tradition. The paper generally addresses the complex historical background of legacies and fideicommissa in Roman law and points to the legal sources through which they were formed, examining as well the contemporary solutions to specific problems concerning legacies that have arisen in judicial practice.