**Magnus Decentius** (died 18 August 353)[^1] was *[[Caesar (title)|caesar]]* of the [[Western Roman Empire]] from 350 to 353, under his brother [[Magnentius]].

## History

Nothing is known of Decentius prior to 350.[^2] Magnentius usurped power from [[Constans]] on 18 January 350, and elevated Decentius as *caesar* later that year, perhaps in July or August.[^2] He was appointed [[Roman consul|consul]] in 352.[^2] In the following year, after losing the [[Battle of Mursa Major]], Magnentius' exactions to finance the war drove [[Gaul]] into revolt against his dictatorial rule, and Decentius was expelled from the capital, [[Trier|Treveri]], by revolt leader [[Poemenius (usurper)|Poemenius]].

The [[Alemanni]] began to invade the province, perhaps at the instigation of the emperor [[Constantius II]], in order to increase pressure on the usurper.[^3] Decentius, who led his brother's forces in the north, was defeated in a pitched battle by the Alemannic chief [[Chnodomarius|Chnodomar]], and besieged in [[Sens]].[^4] There, news reached him of Constantius' victory at the [[Battle of Mons Seleucus]], and the subsequent suicide of Magnentius. Decentius [[Hanged himself|hanged himself]], signalling the end of the civil war.[^5]

## Sources

-   Crawford, Peter (2016). [*Constantius II: Usurpers, Eunuchs, and the Antichrist*](https://books.google.com/books?id=_aJBDQAAQBAJ). Pen & Sword. [[ISBN (identifier)|ISBN]] 978-1-78340-055-3.
-   [[A. H. M. Jones|Jones, A.H.M.]]; [[John Robert Martindale|J.R. Martindale]] & [[John Morris (historian)|J. Morris]] (1971). [*Prosopography of the Later Roman Empire*](https://archive.org/details/prosopography-later-roman-empire/PLRE-I). Vol. 1\. Cambridge University Press. [[ISBN (identifier)|ISBN]] 0-521-07233-6.
-   [[Ammianus Marcellinus]], [*Res Gestae*, XVI](https://penelope.uchicago.edu/Thayer/L/Roman/Texts/Ammian/16*.html)
-   [[Edward Gibbon]] \[1789\] (1932) *[[The History of the Decline and Fall of the Roman Empire]]*. [[The Modern Library]].

## Notes

[^1]: Kienast, Dietmar; [[Werner Eck]]; Matthäus Heil (2017). *Römische Kaisertabelle: Grundzüge einer römischen Kaiserchronologie*. Darmstadt: [[Wissenschaftliche Buchgesellschaft|WBG]]. pp. 305–306\. [[ISBN (identifier)|ISBN]] 978-3-534-26724-8.
[^2]: Kienast, Dietmar; [[Werner Eck]]; Matthäus Heil (2017). *Römische Kaisertabelle: Grundzüge einer römischen Kaiserchronologie*. Darmstadt: [[Wissenschaftliche Buchgesellschaft|WBG]]. pp. 305–306\. [[ISBN (identifier)|ISBN]] 978-3-534-26724-8.
[^3]: Although Crawford merely recorded it with the phrase “is said,”[[Decentius|4]] he seems to accept it as true, later listing it amongst Constantius’ acts that he considered to be "unscrupulous."[[Decentius|5]]
[^4]: [[Decentius|Crawford 2016]], p. 81.
[^5]: Gibbon, chap. XVIII., p. 597.