Hadrokirus martini is an extinct species of true seal (Phocidae) that lived on the coast of Peru about 6 million years ago. It was found in the Pisco Formation, together with other marine animals such as crustaceans, sharks, coastal birds, whales and aquatic sloths. The distinguishing feature of the seal was its teeth: they were extremely robust, hence the name (hadros, "stout" in Greek; kiru, tooth in Quechua). It is assumed that Hadrokirus martini was durophagous; its diet probably comprised crustaceans, small bivalves and other shelled animals, similar to that of the living sea otter. The living seals most closely related to Hadrokirus martini are the Antarctic seals.