Endym'ion, in Greek myth, a youth famous for his beauty and never-ending sleep. As he slept on Mt. Latmos in Caria, his beauty warmed the cold heart of Selene (the moon) who came down to kiss him and to lie by his side. It was said that Selene had sent him to sleep that she might kiss him without his knowing. On this story Keats wrote his well-known poem Endymion.