Xenophon (Ancient Greek: Ξενοφῶν, Xenophōn; c. 430 – 354 BC), son of Gryllus, of the deme Erchia of Athens, also known as Xenophon of Athens, was a Greek historian, soldier, mercenary, philosopher and a contemporary and admirer of Socrates. He is known for his writings on the history of his own times, the 4th century BC, preserving the sayings of Socrates, and descriptions of life in ancient Greece and the Persian Empire.

Xenophon's birth date is uncertain, but most scholars agree that he was born around 431 BC near the city of Athens. Xenophon was born into the ranks of the upper classes, thus granting him access to certain privileges of the aristocracy of ancient Attica. While a young man, Xenophon participated in the expedition led by Cyrus the Younger against his older brother, king Artaxerxes II of Persia, in 401 BC. Xenophon writes that he had asked the veteran Socrates for advice on whether to go with Cyrus, and that Socrates referred him to the divinely inspired Delphic oracle. Xenophon's query to the oracle, however, was not whether or not to accept Cyrus' invitation, but "to which of the gods he must pray and do sacrifice, so that he might best accomplish his intended journey and return in safety, with good fortune". The oracle answered his question and told him to which gods to pray and sacrifice. When Xenophon returned to Athens and told Socrates of the oracle's advice, Socrates chastised him for asking so disingenuous a question.

Nicholas "Nick" Xenophon (born Nicholas Xenophou 29 January 1959) is a South Australian barrister, anti-gambling campaigner and politician. He attended Prince Alfred College, and studied law at the University of Adelaide, attaining his Bachelor of Laws in 1981. Xenophon established and became principal of his own law firm, Xenophon & Co. in 1984. Between 1994 and 1997 he served as president of the South Australian branch of the Australian Plaintiff Lawyers' Association.

No Pokies, the name of his independent ticket in the South Australian Legislative Council, garnered 2.9 percent of the statewide vote at the 1997 state election electing himself on preferences, and 20.5 percent at the 2006 election (or 2.5 quotas), which was unexpected by political commentators. He was elected to the Australian Senate at the 2007 federal election, receiving 14.8 percent. This was still over one full Senate quota, gaining election without the need for preferences. Xenophon shared the balance of power with the Greens and Family First during the 2008–11 Senate parliamentary session, with the Greens holding the sole balance of power since July 2011. Whilst his original 1997 platform centred on anti-pokies, he has since become an advocate in many other areas. Xenophon has been reported in the media as "left-of-centre", while Hansard reveals that Xenophon and the Greens have found common ground on a number of issues.