Robber flies form a distinct part of the global insect fauna with approximately 7000 described species that have attracted researchers’ attention for centuries. The phylogenetic relationships within Asilidae are poorly understood and have never been addressed in a comprehensive morphological analysis. In the present study, morphological features of the imagines used in classifications by past authors are combined with previously unreported character complexes to resolve relationships among 158 species sampled from 139 genera from all over the world. All currently recognised 11 subfamily taxa and 39 of the 42 tribal taxa are represented. Of particular interest to this project is the position of Leptogastrinae within Asilidae, a taxon comprising robber flies of rather unusual morphology and which has been considered as sister-group to Asilidae by previous authors. In this analysis, Asilidae is supported as monophyletic based on a number of autapomorphies with respect to the 17 Asiloidea species included as outgroup taxa. The higher-level relationships are well resolved and a taxon comprising (Laphriinae + Laphystiinae) is the sister-group to the remaining Asilidae. The analysis supports monophyly of five Asilidae subfamily taxa and non-monophyly of six. Leptogastrinae is monophyletic and nested deep within Asilidae, contradicting its previous placement as adelphotaxon to all other Asilidae. Acronyches maya is supported as the sister-taxon of Leptogastrinae; sharing with it a number of autapomorphic features. Comments on a higher-level classification of Asilidae, including the subdivision of the paraphyletic Dasypogoninae and Stenopogoninae, are made based on the morphological synapomorphies resulting from this hypothesis.