Aratus (/əˈreɪtəs/; Ancient Greek: Ἄρᾱτος ὁ Σολεύς; ca. 315 BC/310 BC – 240 BC) was a Greek didactic poet. His major extant work is his hexameter poem Phenomena (Ancient Greek: Φαινόμενα, Phainómena, "Appearances"; Latin: Phaenomena), the first half of which is a verse setting of a lost work of the same name by Eudoxus of Cnidus. It describes the constellations and other celestial phenomena. The second half is called the Diosemeia (Διοσημεῖα "Forecasts"), and is chiefly about weather lore. Although Aratus was somewhat ignorant of Greek astronomy, his poem was very popular in the Greek and Roman world, as is proved by the large number of commentaries and Latin translations, some of which survive.
There are several accounts of his life by anonymous Greek writers, and the Suda and Eudocia also mention him. From these it appears that he was a native of Soli in Cilicia, (although one authority says Tarsus). He is known to have studied with Menecrates in Ephesus and Philitas in Cos. As a disciple of the Peripatetic philosopher Praxiphanes, in Athens, he met the Stoic philosopher Zeno, as well as Callimachus of Cyrene and Menedemus, the founder of the Eretrian school.