In Greek mythology, Benthesikyme was a sister of Poseidon. She raised Eumolpus, son of Chione and Poseidon.

Chione, pregnant with Eumolpus, was frightened of her father's reaction so she threw the baby into the ocean. Poseidon looked after him and brought him to shore in Ethiopia, where his sister, Benthesikyme, raised the child, who then married one of her daughters. Eumolpus however loved a different daughter and Benthesikyme sent him in exile to Thrace.