Comparative studies require information on phylogenetic relationships, but complete species-level phylogenetic trees of large clades are difficult to produce. One solution is to combine algorithmically many small trees into a single, larger supertree. Here we present a virtually complete, species-level phylogeny of the marsupials (Mammalia: Metatheria), built by combining 158 phylogenetic estimates published since 1980, using matrix representation with parsimony. The supertree is well resolved overall (73.7%), although resolution varies across the tree, indicating variation both in the amount of phylogenetic information available for different taxa, and the degree of conflict among phylogenetic estimates. In particular, the supertree shows poor resolution within the American marsupial taxa, reflecting a relative lack of systematic effort compared to the Australasian taxa. There are also important differences in supertrees based on source phylogenies published before 1995 and those published more recently. The supertree can be viewed as a meta-analysis of marsupial phylogenetic studies, and should be useful as a framework for phylogenetically explicit comparative studies of marsupial evolution and ecology.