Ramalina ketner-oostrae is a species of saxicolous (rock-dwelling), fruticose lichen in the family Ramalinaceae.

[1] It is found in the remote tropical island of Saint Helena, where it occurs on cliffs.

The type specimen was collected by the author south of Gregory's Battery at an elevation of 300 m (980 ft); there, it was found growing on basalt.

The branches are thin, flattened, papery, and fan-shaped (flabellate) in outline, lacking pseudocyphellae.

The species epithet honours Dutch lichenologist and ecologist Rita Ketner-Oostra.