This study unravels the symbionts of the lichenized fungus Diorygma aeolum with its Trentepohlia photobiont from the Western Ghats (India). Phylogenetic positioning of the mycobiont and photobiont was assessed by integrating morphology, thallus chemistry, and DNA sequence data. In the phylogenetic analysis of the mycobiont using mtSSU, nuLSU, and RPB2 sequences, D. aeolum was placed in a clade closely related to D. karnatakense. Based on the study, the species D. albovirescens and D. saxicola under D. aeolum were synonymized by re-examining type material and protologue. The ITS-based phylogenetic analysis placed its photobiont Trentepohlia sp. in a clade containing the unidentified Trentepohlia isolates TreFl63 (from Graphis sp., Brazil), TreFl149 (from Arthonia atra, UK), S16_Gp (from Graphis propinqua, Argentina), TreFl51 (from Diorygma pruinosum, Brazil), and TreFl61 (from Graphis sp., Brazil), suggesting this clade to be entirely lichenized. Keywords: Lichenized fungi, Symbiosis, Synonymization, Polyphasic taxonomy.