Ctenidium (plural: ctenidia) may refer to: Ctenidium (mollusc) (plural: ctenidia), a comb-like gill, part of the respiratory system of molluscs Ctenidium (plural: ctenidia), a row of peg-like spines in some insects (pronotal ctenidium; genal ctenidium) Ctenidium (plant), a genus of mosses in the family Hylocomiaceae Ctenidia (beetle), a genus of beetles in the family Mordellidae