Lasiodiplodia species are commonly as endophytes, saprobes and pathogens in tropics and subtropics. During an investigation of Botryosphaeriaceae in Thailand, two Lasiodiplodia taxa were isolated. Morphological characteristics and phylogenetic analyses based on combined ITS, tef and tub2 sequence data support the establishment of a novel species, Lasiodiplodia chiangraiensis, isolated from woody hosts. Lasiodiplodia chiangraiensis is phylogenetically close to L. iraniensis and L. thailandica, but represents a distinct lineage. The new species could be distinguished from extant Lasiodiplodia species by its mature conidial dimensions. A detailed description and illustration are provided, as well as an updated phylogenetic tree (ITS, tef and tub2) including all species (with available molecular data) of Lasiodiplodia. In addition, the accepted genera in Botryosphaeriaceae based on recent studies are given.