Using a multicharacter approach and numerical cladistic computer programs a phylogenetic analysis is made of a newly defined order Halichondrida (which includes all Halichondrida and parts of the Axinellida sensu Lévi, 1973), with emphasis on the newly defined family Halichondriidae (which includes the families Halichondriidae and Hymeniacidonidae sensu Lévi, 1973, and some genera formerly assigned to the Axinellidae and Desmoxyidae). The newly defined order consists of the “old” families Axinellidae/Bubaridae and Desmoxyidae, a “new” family Dictyonellidae (containing Dictyonella, Acanthella, Liosina and Dactylella), and the new concept of the family Halichondriidae. On the basis of numerous specimens, including many type and other original material from all parts of the world oceans, the latter group has been analyzed in depth. Next to classical morphological characters also biochemical data (secondary metabolites) were used. This resulted in the recognition of several discrete generic groups, viz. Axinyssa + Collocalypta, Myrmekioderma + Didiscus, Spongosorites, Topsentia + Epipolasis + Petromica, Ciocalypta + Amorphinopsis, and + Hymeniacidon Halichondria. A revision comprising definitions of and remarks on all genera, including all junior synonyms, of the newly defined Halichondriidae concludes the paper.