This volume is the sixth in a series of Taxonomic Guides to the Stick Insects of South East Asia and the ninth book on stick insects by the author. It is the second volume to report on the stick insects of Sumatra. This book follows the concept of the first five volumes by the author in this series: which are A Taxonomic Guide to Stick Insects of Borneo (2016), A Taxonomic Guide to Stick Insects of Borneo Volume II (2017), A Taxonomic Guide to Stick Insects of Singapore (2017), A Taxonomic Guide to Stick Insects of Sumatra (2018) and A Taxonomic Guide to Stick Insects of Borneo Volume III (2019). This sixth volume is once again lavishly illustrated with beautiful colour photographs of the various species of stick insects being discussed in the book. A Taxonomic Guide to Stick Insects of Sumatra Volume I (2018) listed 170 species, from 64 genera or subgenera, with 60 new species or subspecies and 4 new genera from Sumatra. This latest volume, A Taxonomic Guide to Stick Insects of Sumatra Volume II (2020) lists 21 new species or subspecies, one new genus, the designation of 3 lectotypes, one neotype designation, one new synonymous genus, 9 synonymous species, 5 revised specific statuses, 20 new combination names, the description of the unknown sex of 7 species, and 3 new records for Sumatra. The number of recognized species in Sumatra listed stands at 190. This latest research on the phasmid fauna of Sumatra, and indeed in the whole of South East Asia will enable conservationists, entomologists and amateur enthusiasts world-wide to better understand these insects and plan their conservation as well as the preservation of their habitats in a more scientific way.