Editing List of Roman emperors (section)

=== Tetrarchy (284–324) ===
{{Main|Tetrarchy}}
{{Legend|#EBEBEB|({{Hash-tag}}) – Ambiguous legitimacy{{Efn|name=ambig}}}}

{| class="wikitable plainrowheaders" style="width:100%; text-align:center"
|+ {{Sronly|Tetrarchy}}
! scope=col width="7%" | Portrait
! scope=col width="17%" | Name
! scope=col width="26%" | Reign
! scope=col width="25%" | Succession
! scope=col width="25%" | Life details

|-
| [[File:Head of Diocletian, Getty Museum (cropped).jpg|frameless|100px|alt=bust]]
! scope=row style="text-align:center; background:#F8F9FA" | '''[[Diocletian]]''' "Jovius"<br/>{{Small|''Gaius Aurelius Valerius Diocletianus''}}
| 20 November 284 – 1 May 305<br/>{{Small|({{Age in years, months and days|284|11|20|305|5|1}})<br/>'''Whole'''; then '''East'''}}
| Commander of the imperial bodyguard, acclaimed by the army after death of [[Numerian]], and proceeded to defeat Numerian's brother, [[Carinus]], in battle
| 22 December {{Circa}} 243 – 3 December {{Circa}} 311<br/>{{Small|(aged approx.&nbsp;68)}}<hr/>Began the last [[Diocletianic Persecution|great persecution]] of Christianity. First emperor to voluntarily abdicate. Died in unclear circumstances, possibly suicide{{Sfnm|1a1=Barnes|1pp=4, 30–32|2a1=Kienast|2a2=Eck|2a3=Heil|2pp=257–258|3a1=Grant|3p=204}}

|-
| [[File:Musée Saint-Raymond - 2017-09-02 - Inv. Ra 34b - 4654 (cropped).jpg|100px|alt=bust]]
! scope=row style="text-align:center; background:#F8F9FA" | '''[[Maximian]]''' "Herculius"<br/>{{Small|''Marcus Aurelius Valerius Maximianus''}}
| 1 April 286{{efn|The chronology of Maximian's career is disputed. Some authors argue that he was promoted to ''augustus'' without ever being ''caesar'', as claimed by many others. Another possible date for his accession as emperor (and the first division of the Roman Empire) is 13 December 285.{{sfn|Burgess|2023}}}} – 1 May 305<br/>{{Small|({{Age in years, months and days|286|4|1|305|5|1}}; '''West''')}}<br/>November 306 – 11 November 308<br/>{{Small|(2 years; '''Italy''')}}
| Elevated by Diocletian, ruled the [[Western Roman Empire|western provinces]]
| c. 250 – c. July 310<br/>{{Small|(aged approx.&nbsp;60)}}<hr/>Abdicated with Diocletian, later trying to regain power with, and then from, [[Maxentius]], before being probably killed on orders of [[Constantine&nbsp;I]]{{Sfnm|1a1=Barnes|1pp=4, 13, 32, 34|2a1=Kienast|2a2=Eck|2a3=Heil|2pp=262–263|3a1=Grant|3pp=210–212}}

|-
| [[File:Portrait of Galerius, Thessaloniki (head).jpg|100px]]
! scope=row style="text-align:center; background:#F8F9FA" | '''[[Galerius]]'''<br/>{{Small|''Gaius Galerius Valerius Maximianus''}}
| 1 May 305 – May 311<br/>{{Small|(6 years; '''East''')}}
| Elevated to ''caesar'' in 293 by Diocletian, succeeded as eastern ''augustus'' upon Diocletian's abdication
| c. 258 – May 311<br/>{{Small|(aged approx.&nbsp;53)}}<hr/>Died of natural causes{{Sfnm|1a1=Kienast|1a2=Eck|1a3=Heil|1pp=272–273|2a1=Barnes|2pp=4–6, 46|3a1=Grant|3pp=221–222}}

|-
| [[File:Constantius Chlorus Ny Carlsberg Glyptotek IN836 (cropped).jpg|100px|alt=bust]]
! scope=row style="text-align:center; background:#F8F9FA" | '''[[Constantius Chlorus|Constantius I]]''' "Chlorus"<br/>{{Small|''Marcus Flavius Valerius Constantius''}}
| 1 May 305 – 25 July 306<br/>{{Small|({{Age in years, months and days|305|5|1|306|7|25}}; '''West''')}}
| Maximian's relation by marriage, elevated to ''caesar'' in 293 by Diocletian, succeeded as western ''augustus'' upon Maximian's abdication
| 31 March {{Circa}} 250 – 25 July 306<br/>{{Small|(aged approx. 56)}}<hr/>Died of natural causes{{Sfnm|1a1=Kienast|1a2=Eck|1a3=Heil|1p=269|2a1=Barnes|2pp=35–36|3a1=Grant|3pp=216–218|4a1=ODB|4p=524–525}}

|-
| [[File:Severus II Aureus Joanneum.jpg|100px|alt=coin]]
! scope=row style="text-align:center; background:#F8F9FA" | '''[[Severus II]]'''{{Small|<br/>''Flavius Valerius Severus''}}
| August 306 – March/April 307<br/>{{Small|(c. 8 months; '''West''')}}
| Elevated to ''caesar'' in 305 by Maximian, promoted to western ''augustus'' by Galerius upon Constantius&nbsp;I's death
| Unknown – September 307<hr/>Surrendered to Maximian and Maxentius, later murdered or forced to commit suicide{{Sfnm|1a1=Kienast|1a2=Eck|1a3=Heil|1p=278|2a1=Barnes|2pp=4–5, 38–39|3a1=Grant|3pp=223–224}}

|-
| [[File:Portrait of Maxentius (SK Dresden Hm 406) 01 (cropped).jpg|100px|alt=bust]]
! scope=row style="text-align:center; background:#F8F9FA" | '''[[Maxentius]]'''<br/>{{Small|''Marcus Aurelius Valerius Maxentius''}}
| 28 October 306 – 28 October 312<br/>{{Small|(6 years; '''Italy''')}}
| Son of Maximian and son-in-law of Galerius, seized power in Italy with support of the [[Praetorian Guard]] and his father after being passed over in the succession. Not recognized by the other emperors
| c. 283 – 28 October 312<br/>{{Small|(aged approx. 29)}}<hr/>Died at the [[Battle of the Milvian Bridge]], against [[Constantine&nbsp;I]]{{Sfnm|1a1=Kienast|1a2=Eck|1a3=Heil|1p=279|2a1=Grant|2pp=224–226|3a1=Barnes|3pp=12–13, 34}}

|-
| [[File:Bust of Licinius, Kunsthistorisches Museum (cropped).jpg|100px|alt=bust]]
! scope=row style="text-align:center; background:#F8F9FA" | '''[[Licinius]]'''<br/>{{Small|''Valerius Licinianus Licinius''}}
| 11 November 308 – 19 September 324<br/>{{Small|({{Age in years, months and days|308|11|11|324|9|19}})<br/>'''West'''; then '''East'''}}
| Elevated by Galerius to replace Severus, in opposition to Maxentius. Defeated [[Maximinus Daza]] in a civil war to become sole emperor of the [[Eastern Roman Empire|East]] in 313
| c. 265 – early 325<br/>{{Small|(aged approx. 60)}}<hr/>Defeated, deposed and put to death by [[Constantine&nbsp;I]]{{Sfnm|1a1=Kienast|1a2=Eck|1a3=Heil|1p=282|2a1=Barnes|2pp=6–7, 43–44|3a1=Grant|3pp=235–237}}

|-
| [[File:Aureus of Maximinus II (obverse).jpg|100px|alt=coin]]
! scope=row style="text-align:center; background:#F8F9FA" | '''[[Maximinus Daza|Maximinus II]]''' "Daza"<br/>{{Small|''Galerius Valerius Maximinus''}}
| 310 – c. July 313<br/>{{Small|(3 years; '''East''')}}
| Nephew of Galerius, elevated to ''caesar'' by Galerius in 305, and acclaimed as ''augustus'' by his troops in 310
| 20 November c. 270 – c. July 313<br/>{{Small|(aged approx. 42)}}<hr/>Defeated in civil war against [[Licinius]], died shortly afterwards{{Sfnm|1a1=Kienast|1a2=Eck|1a3=Heil|1p=276|2a1=Barnes|2pp=6–7, 39|3a1=Grant|3pp=238–240}}

|-
| [[File:Valerius Valens coin (transparent background).png|100px|alt=coin]]
! scope=row style="text-align:center; background:#F8F9FA" | '''[[Valerius Valens]]'''{{Efn|name=valensandmartinian|Legitimately appointed as co-emperor by Licinius, though as western emperor (in opposition to Constantine&nbsp;I). Referred as ''caesar'' in literary sources, but called ''augustus'' in coinage. Did not actually rule anything given that Licinius did not control the west.{{Sfn|Vagi|1999|pp=466–467}}}}<br/>{{Small|''Aurelius Valerius Valens''}}
| October 316 – c. January 317<br/>{{Small|(c. 2–3 months; '''East'''*)}}
| Frontier commander in [[Dacia Ripensis|Dacia]], elevated by Licinius in opposition to Constantine&nbsp;I
| Unknown – 317<hr/>Executed in the lead-up to a peace settlement between Licinius and Constantine{{Sfnm|1a1=Kienast|1a2=Eck|1a3=Heil|1p=284|2a1=Barnes|2p=15}}

|-
| [[File:Martinian coin (transparent background).png|100px|alt=coin]]
! scope=row style="text-align:center; background:#F8F9FA" | '''[[Martinian (emperor)|Martinian]]'''{{Efn|name=valensandmartinian}}<br/>{{Small|''Mar. Martinianus''}}
| July – 19 September 324<br/>{{Small|(2 months; '''East'''*)}}
| A senior bureaucrat, elevated by Licinius in opposition to Constantine&nbsp;I
| Unknown – Spring 325<hr/>Deposed by Constantine and banished to [[Cappadocia]], later executed{{Sfnm|1a1=Kienast|1a2=Eck|1a3=Heil|1p=285|2a1=Barnes|2p=15}}

|}