Diorygma sticticum is a species of corticolous (bark-dwelling) script lichen in the family Graphidaceae.

Diorygma sticticum was first described as a new species by lichenologists Jutarat Sutjaritturakan, Klaus Kalb, and Robert Lücking in 2011.

The type specimen was found in Khao Yai National Park in Nakhon Ratchasima province, Thailand.

When viewed in cross-section, the thallus reveals an upper cortex measuring 10–15 μm thick, an uneven algal layer, and groups of calcium oxalate crystals.

These lirellae have a distinct white thalline margin and a concealed to partly exposed, pale brown disc that is thickly white-pruinose.