Hormidium is a group of orchids whose various species have been transferred to Encyclia, Epidendrum, Homalopetalum, Lepanthes, and Prosthechea.
Hormidium can also refer to:
A genus of algae, an illegitimate name whose application caused confusion, now included in the Prasiolaceae Klebsormidium, a genus of filamentous charophyte green algae Epidendrum subg. Hormidium, a subgenus of Epidendrum
See also Homidium or Ethidium bromide Horminum, a genus of flowering plants in the family Lamiaceae