Résumé : In this paper, we present efficient ways of encoding multicast trees. Multicast tree encodings provide a convenient way of performing stateless and explicit multicast routing in networks and overlays. We show the correspondence of multicast trees to theoretical tree data structures and give lower bounds on the number of bits needed to represent multicast trees. Our encodings can be used to represent multicast trees using both node identifiers and link indexes and are based on balanced parentheses representation of tree data structures. These encodings are almost space optimal and can be read and processed efficiently. We evaluate the length of these encodings on multicast trees in generated and real topologies.