Cleanthes (circa 331-232 bc), Stoic philosopher and poet of ancient Greece, born in Asia Minor. While supporting himself by manual labor, he attended the lectures of the Stoic philosopher Zeno and became Zeno's successor as leader of the Stoic school after about 263 bc. Of the more than 50 works he is said to have written, only fragments are extant; the most important of these is called the “Hymn to Zeus.”