This study is the first comprehensive systematic study on the python genus Leiopython Hubrecht 1879 native to New Guinea. The taxonomic arrangement recently made is critically reviewed, and proper descriptions for taxa herein recognized as valid are provided. Twenty external morphological characters were recorded from 90 preserved specimens from throughout most of the distribution of the genus. Thirteen characters were used with principal coordinate analysis to test the diversity of populations from different distributions. Additional evidence for some species was obtained by maximum parsimony and maximum likelihood analysis of mitochondrial DNA sequences (cytochrome b gene) taken from GenBank. Besides three conventional taxa, two new species from the mainland, and one new island species were recognized in accordance with the evolutionary species concept. Additionally, a new locality record is provided.