小居鲁士，波斯王子，为大流士二世所生，公元前401年，小居鲁士从小亚细亚起兵叛乱，率领约一万一千七百名希腊雇佣兵东进位争夺王位，被其兄阿尔塔薛西斯二世所败，但他所雇的希腊雇佣兵却成功退却回希腊本土，这件事被色诺芬记录在他的《长征记》里。

Cyrus the Younger (Old Persian: ), son of Darius II of Persia and Parysatis, was a Persian prince and general. His birth date is unknown, but he died in 401 BC after a failed battle to oust his brother, Artaxerxes II, from the Persian throne.

The history of Cyrus and of the retreat of the Greeks is told by Xenophon in his Anabasis. Another account, probably from Sophaenetus of Stymphalus, was used by Ephorus. Further information is contained in the excerpts from Artaxerxes II's physician, Ctesias, by Photius; Plutarch’s Lives of Artaxerxes II and Lysander; and Thucydides' History of Peloponnesian War. These are the only early sources of information on Cyrus the Younger.