Colletotrichum has a wide host range and distribution and its species are pathogens, endophytes and saprobes. Investigations of Colletotrichum species in both tropical and temperate regions are still needed as much novelty remains to be discovered. A multi-locus phylogenetic analyses of ITS, GAPDH, CHS-1, ACT and TUB2 sequence data combined with morphology, revealed a new species, C. acidae on Phyllanthus acidus, belonging to the C. truncatum species complex. A new Russian record for C. dematium on Iris sp. was also revealed. A combination of sequence data handling tools in the ARB database was used for the phylogenetic analyses and is provided in the appendix. The new species is described and illustrated in this paper and compared with taxa in the C. truncatum species complex.