Background Thunbergia grandiflora belongs to the family Acanthaceae and is a widely distributed dicotyledonous plant in tropical and subtropical regions. Three isolates of Allophoma ( Dothideomycetes , Pleosporales , Didymellaceae ) were collected from leaves of T. grandiflora in Guangxi Province, China. New information Phylogenetic analyses of a combined ITS–LSU– rpb2 – tub2 dataset indicate that one of our three strains represents an undescribed species with close affinity to A. minor and the other two strains clustered amongst other isolates of A. pterospermicola . Evidence from morphology and sequence analysis indicates that GUCC 2070.7 is a new species that we introduce here as A. thunbergiae . This is the first report about taxa of Allophoma from this host plant.