弗拉维乌斯·克劳狄乌斯·尤利安努斯（拉丁语：Flavius Claudius Julianus，331年－363年6月26日），英文作朱利安（英语：Julian），君士坦丁王朝的罗马皇帝，361年-363年在位。有时候他被称为尤利安二世，以与193年在位的狄图斯·尤利安努斯区分。

他在位期间，由于他对希腊哲学的热爱，让他赢得了哲学家尤利安（ Julian the Philosopher）的称号。尤利安出生就受洗，在严格基督教教育下长大，但后来却转向希腊罗马的传统多神信仰。他师承于新柏拉图主义，崇信神秘仪典，支持宗教信仰自由，反对将基督教信仰视为国教，因此被基督教会称为背教者尤利安（Julian the Apostate）。他在位期间努力推动多项行政改革，是罗马帝国最后一位多神信仰的皇帝。

Julian (Latin:Flavius Claudius Iulianus Augustus, Greek:Φλάβιος Κλαύδιος Ἰουλιανὸς Αὔγουστος; 331/332  – 26 June 363), also known as Julian the Apostate, was Roman Emperor from 361 to 363, as well as a notable philosopher and author in Greek.

A member of the Constantinian dynasty, Julian became Caesar over the western provinces by order of Constantius II in 355 and in this role campaigned successfully against the Alamanni and Franks. Most notable was his crushing victory over the Alamanni in 357 at the Battle of Argentoratum (Strasbourg), leading his 13,000 men against a Germanic army three times larger. In 360 in Lutetia (Paris) he was proclaimed Augustus by his soldiers, sparking a civil war between Julian and Constantius. Before the two could face each other in battle, however, Constantius died, after naming Julian as his rightful successor. In 363, Julian embarked on an ambitious campaign against the Sassanid Empire. Though initially successful, Julian was mortally wounded in battle and died shortly thereafter.