Cytospora is a species-rich and globally distributed genus in Diaporthales, characterized by hyaline, aseptate, and allantoid ascospores and conidia. Many species in this genus are recognized as important plant pathogens that cause branch cankers on a wide range of hosts. Recent taxonomic revisions, integrating morphological and molecular phylogenetic data, have clarified the generic limits of Cytospora, resulting in the recognition of three groups and eight types in the teleomorph and three groups and thirteen types in the anamorph, as well as ten species complexes. In this study, canker diseases on Populus szechuanica var. tibetica and Salix lasiogyne were investigated in Xizang, China. Species identification was conducted using a polyphasic approach combining morphological characteristics and multi-locus phylogenetic analyses based on ITS, act, rpb2, tef1, and tub2 sequences. Consequently, two new species, Cytospora chayuensis from the C. leucostoma species complex and C. sinopopuli from the C. kantschavelii species complex, are introduced herein. This study contributes to knowledge of Cytospora species diversity and provides foundational data for the management of poplar and willow canker diseases.