Parmotrema marcellianum is a species of saxicolous (rock-dwelling), foliose lichen in the family Parmeliaceae.

[1] Found on the Galápagos Islands, it was formally described as a new species in 2019 by lichenologists Frank Bungartz and Adriano Spielmann.

The type specimen was collected from Cerro Ventanas on Floreana Island at an altitude of 424 m (1,391 ft); there, it was found overgrowing pebbles on sun-, wind-, and rain-exposed ground.

The species epithet honours the authors' colleague Marcelo Pinto Marcelli, "in recognition of his work on the lichen family Parmeliaceae".

It produces many soralia, which are capitate and stalked and grow at the tips of short to elongate lobes (called clavulae).