Characium marinum is a species of green algae (Chlorophyta).

Characium marinum is a microscopic unicellular elongated oval algae growing attached epiphytically by a stalk various algae.

[2] and eastern Canada[1] Recorded from Svalbard (Norway), Sweden, once in Ireland County Down,[3] twice in Great Britain, under-recorded.

[1] The taxonomic status of this alga is unclear.

According to the marine biologist T. Levring, Characium marinum probably represents germlings of Cladophora, a genus of marine algae.