Syennesis III (Ancient Greek: Συέννεσις) was a ruler of ancient Cilicia in the 5th century BCE.

Syennesis was a contemporary of Artaxerxes II of Persia, and when Cyrus the Younger, marching against Artaxerxes in 401 BCE, arrived at the borders of Cilicia, he found the passes guarded by Syennesis, who, however, withdrew his troops on receiving intelligence that the force advanced by Cyrus under Meno had already entered Cilicia, and that the combined fleet of the Lacedaemonians and the prince, under Samius and Tamos, was sailing round from Ionia.

When Cyrus reached Tarsus, the Cilician capital, he found that Meno's soldiers had sacked the city, and commanded Syennesis to appear before him. Syennesis had fled for refuge to a stronghold among the mountains, but he was induced by his wife, Epyaxa, to obey the summons of Cyrus. Here he received gifts of honor from Cyrus, whom he supplied in his turn with a large sum of money and a considerable body of troops under the command of one of his sons.

At the same time, however, Syennesis took care to send his other son to Artaxerxes, to represent his meeting with Cyrus as having been something he'd been forced to do, while his heart all the time was with the king, Artaxerxes. From Xenophon's telling it appears that Syennesis at this time, though really a vassal of Persia, affected the tone of an independent sovereign.^[1][2][3]

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  Possible coin of Syennesis, Tarsos. Circa 425-400 BC. Satrap on horseback riding left; behind, eagle perched left on branch; monogram below / Archer in kneeling-running stance right, drawing bow; monogram behind.

v t e Rulers in the Achaemenid Empire
Family tree - Achaemenid Kingdom
Kings of Kings of the Achaemenid Empire	Achaemenes Ariaramnes Arsames Teispes Cyrus I Cambyses I Cyrus the Great Cambyses II Bardiya Darius the Great Xerxes I Artaxerxes I Xerxes II Sogdianus Darius II Artaxerxes II Mnemon Artaxerxes III Ochus Artaxerxes IV Arses Darius III Codomannus Artaxerxes V Bessus
Satraps of Lydia	Tabalus Mazares Harpagus Oroetus Bagaeus Otanes Artaphernes I Artaphernes II Pissuthnes Tissaphernes Cyrus the Younger Tissaphernes Tithraustes Tiribazus Struthas Autophradates Spithridates
Satraps of Hellespontine Phrygia	Mitrobates Megabazus Megabates Oebares II Artabazus I Pharnabazus I Pharnaces II Pharnabazus II Ariobarzanes Artabazus II Pharnabazus III Arsites
Satraps of Cappadocia	Datames Ariamnes I Mithrobuzanes Ariarathes I
Greek Governors of Asia Minor cities	Miltiades Demaratus Gongylos Eurysthenes Prokles Histiaeus Aristagoras Themistocles Archeptolis Aridolis Amyntas II Philiscus
Dynasts of Lycia	Kheziga Kybernis Kuprlli Harpagus Teththiweibi Kheriga Kherei Arbinas Artembares Artumpara Mithrapata Perikle
Dynasts of Caria	Lygdamis I Artemisia Pisindelis Lygdamis II Adusius (satrap) Hecatomnus Mausolus Artemisia II Idrieus Ada Pixodarus Orontobates
Kings of Macedonia	Amyntas I of Macedon Alexander I of Macedon
Kings of Tyre	Mattan IV Boulomenus Abdemon Evagoras Azemilcus
Kings of Sidon	Eshmunazar I Tabnit Queen Amoashtart (regent) Eshmunazar II Bodashtart Yatonmilk Anysos Tetramnestos Baalshillem I Baana Baalshillem II Abdashtart I Tennes Evagoras II Abdashtart II Abdashtart III
Satraps of Armenia	Artasyrus Orontes I Darius III Orontes II
Satraps of Egypt	Aryandes Pherendates Achaemenes Arsames Pherendates II Sabaces Mazaces
Satraps of Bactria	Hystaspes Dadarsi Masistes Bessus
Satraps of Media	Hydarnes Hydarnes the Younger Atropates
Satraps of Cilicia	Syennesis III Camisares Mazaeus Arsames
Other known satraps	Megabyzus, Abrocomas, Belesys (Syria) Ochus (Hyrcania) Satibarzanes (Aria) Atizyes (Greater Phrygia) Phrataphernes (Parthia) Ariobarzanes (Persis) Abulites (Susiana) Mazaeus (Babylon)
In most territories, Achaemenid rulers were succeeded by Hellenistic satraps and Hellenistic rulers from around 330 BC

 This article incorporates text from a publication now in the public domain: Elder, Edward (1870). "Syennesis". In Smith, William (ed.). Dictionary of Greek and Roman Biography and Mythology. Vol. 3. p. 949.