Twenty-four extant species of snakes, usually referred to as pythonines (sensu Underwood, 1976), are compared in terms of 121 behavioural and external and internal morphological characters. A cladistic analysis of 194 synapomorphies confirms the monophyly of the group, and provides a partially resolved, well-corroborated hierarchy of lineage relationships. That hypothesis obtains without regard to assumptions of additivity or nonadditivity, and only those synapomorphies which delimit clades unambiguously are used to diagnose taxa. Aspidites is demonstrated to be the sister lineage of all other pythonines, and the remaining Australia-New Guinea taxa constitute a paraphyletic assemblage. The South-east Asia-Africa Python forms a highly derived clade. The following binominal monophyletic taxonomy is proposed: Antaresia childreni, A. maculosus, A. perthensis, A. stimsoni, Apodora papuana (n.gen.), Aspidites melanocephalus, A. ramsayi, Bothrochilus boa, Leiopython albertisii, Liasis mackloti, L. olivaceus, Morelia amethistina, M. boeleni, M. carinata, M. oenpelliensis, M. spilota, M. viridis, Python anchietae, P. curtus, P. molurus, P. regius, P. reticulatus, P. sebae, P. timoriensis. The extinct Miocene Morelia antiqua and Montypythonoides riversleighensis from Australia are referred to the synonymy of extant Liasis olivaceus and Morelia spilota, respectively.