Arses (*R̥šā; Ἀρσής), also known by his regnal name Artaxerxes IV (ˌɑrtəˈzɜrksiːz; 𐎠𐎼𐎫𐎧𐏁𐏂𐎠 ; Ἀρταξέρξης), was the twelfth Achaemenid King of Kings from 338 to 336 BC.
Arses ascended the throne, after his father Artaxerxes III—who had caused a resurgence of the Persian Empire—was poisoned by the eunuch Bagoas. The latter put Arses on the throne with the expectation of being able to control him. With the weakening of the Achaemenid Empire from the assassination of Artaxerxes III and the succession of Arses, the Greek league sent troops into Asia in 336.
Arses, in an attempt to free himself from Bagoas' influences, tried to have the eunuch poisoned; but did not succeed, instead succumbing to poison himself at the orders of Bagoas. Bagoas put Arses' cousin Darius III on the throne after him.
He is known as Arses in Greek sources and that seems to have been his real name, but the Xanthus trilingue and potsherds from Samaria report that he took the royal name of Artaxerxes IV, following his father and grandfather.
Arses is the Greek form of the Old Persian R̥šā, which is also attested in the Avestan form Aršan- and is used in multiple Old Persian compound-names, such as , , and . The term is linguistically related to Greek , meaning "male, manly".
Arses was the youngest son of Artaxerxes III and his wife Atossa. Arses had several brothers, only one whose name is attested, a certain Bisthanes. Persia was experiencing a resurgence under Artaxerxes III, who reorganized his empire, and suppressed revolts throughout the country. However, the fortunes of Persia came to an abrupt end in autumn of 338, when Artaxerxes III was murdered by the ambitious eunuch and chiliarch Bagoas, who had the king poisoned. Artaxerxes III's early death proved to be a problematic issue for Persia, and may have played a role in the weakening of the country. The majority of Artaxerxes III's sons, with the exception of Arses and Bisthanes, were also murdered by Bagoas. Bagoas, who wanted to be kingmaker, put the young Arses on the throne.