Three species of Opegrapha Ach. are described as new. The sympatric O. australis and O. oraria occur on coastal siliceous rocks in eastern Victoria and southern New South Wales, both having thin, pale and inconspicuous thalli, with short, narrow, mostly sessile black lirellae with a basally closed, largely carbonized proper excipulum, a shallow, non-inspersed hymenium and Varia-type asci. However, the former has (3–)5-septate ascospores 12–18 × 2.5–4.5 μm, while those of O. oraria are mostly 3-septate and 12–18 × 3–6 μm. Opegrapha howeana, from sheltered basalt in lowland, subtropical forest in Lord Howe Island, has a thin, delicately rimose, greenish grey thallus, elongate and simple to sparingly branched, adnate to subsessile lirellae with rounded or truncate ends, a slit-like disc and a closed excipulum base, broad asci, mainly 7-septate ascospores, 24–36 × 5.5–9 μm, most with enlarged median cells and a distinct perispore. Two other species, O. diaphoriza Nyl. and O. spodopolia Nyl., are reported for the first time from rocky seashores in southern New South Wales, the latter also in eastern Victoria.