Hypoglossum hypoglossoides, known as under tongue weed,[1] is a small red marine alga in the family Delesseriaceae.

Spermatangial sori are formed on the blades on either side of the midrib.

[2] Found in the littoral and sublittoral on rock or epiphytically on other large algae.

[4] Found on the shores of Ireland, Great Britain, Isle of Man and the Channel Islands.

Further south in Spain and the Mediterranean, as well as North Carolina to Brazil.