Porolithon is a genus of coralline red algae.

The Porolithon are the primary reef building algae.

When coral reefs reach sea level, many corals break under the high energy impact of the waves, while coralline red algae, primarily Porolithon, continuing building and cementing the reef structure.

[3][4][5] The genus currently comprises 24 species, although more have been recently proposed based on genomic analyses.

[6] The type species of this genus, Porolithon onkodes, was originally described in 1897 as Lithothamnion onkodes by Franz Heydrich, but subsequently moved to Porolithon in 1909.