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The Roman legions


Legionary standard (of XXX Ulpia Traiana reenactment group). Photo Jona Lendering.
A Roman legion was an infantry unit consisting of  heavily armed soldiers, equiped with shields, armor, helmets, spears and swords. In the early republic, the strength of a legion was about 3,000 men; there were 4,800 legionaries in the days of Julius Caesar; the twenty-five legions that defended the empire during the reign of Augustus counted more than 5,000 soldiers. They were the backbone of the Roman army, supported by auxiliary troops. Although in the third century, large cavalry units gradually superseded the legions as Rome's most important force, many of them are attested in the fourth and early fifth centuries.

On this site, you will find an alphabetical and chronological catalogue of the imperial legions. An overview of the armies in certain provinces is here.

Geographical overview

Related:
RomanArmy.Com

Ancient-Warfare.com, the online home of Ancient Warfare magazine

Reconstruction of a Roman legionary. Rheinisches Landesmuseum, Bonn (Germany). Photo Marco Prins.
Reconstruction of a Roman legionary (Rheinisches
Landesmuseum, Bonn)

Alphabetical catalogue

The following table catalogue contains only the legions that served under the early empire. Units in italics were part of the army of the emperor Augustus.
 
I Adiutrix
III Parthica
XII Fulminata
I Germanica
IIII Macedonica
XIII Gemina
I Italica
IIII Flavia Felix
XIV Gemina
I Macriana Liberatrix
IIII Scythica
XV Apollinaris
I Minervia
V Alaudae
XV Primigenia
I Parthica
V Macedonica
XVI Gallica
II Adiutrix
VI Ferrata
XVI Flavia Firma
II Augusta
VI Victrix
XVII
II Italica
VII Claudia
XVIII
II Parthica
VII Gemina
XIX
II Traiana Fortis
VIII Augusta
XX Valeria Victrix
III Augusta
VIIII Hispana
XXI Rapax
III Cyrenaica
X Fretensis
XXII Deiotariana
III Gallica
X Gemina
XXII Primigenia
III Italica
XI Claudia
XXX Ulpia Victrix

A Roman legionary (fourth century). Fectio, Houten (Holland).
A Roman legionary (fourth century) (Fectio; ©**)
In the fourth century, we hear of other legions, but at that moment, the legions were no longer the backbone of the Roman army. Their names are included in the following table:
 
I Iulia Alpina
I Pontica
 III Isaura
I Armeniaca
II Iulia Alpina
IIII Italica
I Flavia Constantia
II Armeniaca
IIII Martia
 I Flavia Gallicana
II Brittannica
IIII Parthica
 I Flavia Martis
II Flavia Constantia
V Iovia
I Flavia Pacis
II Flavia Virtutis
V Parthica
I Illyricorum
II Herculia
VI Gallicana
I Iovia
II Isaura
VI Herculia
I Isaura Sagitaria
III Iulia Alpina
VI Hispana
I Martia
III Diocletiana
VI Parthica
I Maximiana
III Flavia Salutis
XII Victrix
I Noricorum
III Herculia

Chronological catalogue


Before Caesar:

Bust of Julius Caesar. Musei Vaticani, Roma (Italy). Photo Jona Lendering.
Julius Caesar
(Musei Vaticani, Rome)

Julius Caesar, 58 BCE


Caesar, 57 BCE:


Caesar, 53 BCE:

  • XIV (reconstituted)
  • XV (destroyed 49-48 in Africa)
  • XVI (destroyed 49-48 in Africa)


Caesar, 52 BCE:


Caesar, 49-48 BCE (using consular numbers):

 
Chronological overview of legions; design Jona Lendering.
Chronological overview of legions

Pansa, 43 BCE:
Mark Antony:

Bust of Augustus as high priest. Museo Nacional de Arte Romano, Mérida (Spain). Photo Marco Prins.
Bust of Octavian/Augustus as high priest. Museo Nacional de Arte Romano, Mérida.

Octavian, 41-40 BCE:
Octavian 30 BCE: Battle in Teutoburg Forest:
  • XVII, XVIII, XIX destroyed
 
Bust of Nero. Glyptothek München (Germany). Photo Marco Prins.
Nero (Glyptothek, Munich)

Caligula
, 39 CE:
Nero, 66:


Nero, 68:

 


Galba, 68:

Bust of Domitian. Museo Arqueológico, Sevilla (Spain). Photo Marco Prins.
Domitian (Museo Arqueológico,  Sevilla)

Vespasian, 70:
Domitian, 83: War against Decebalus, 92: Trajan, 105: Uncertain date:
 
Bust of Septimius Severus. Archaeological Museum, Thessaloniki (Greece). Photo Marco Prins.
Septimius Severus (Archaeological Museum, Thessaloniki)

Marcus Aurelius, 168:
Septimius Severus, 197: Heliogabalus, 220: Severus Alexander, 230?
 
Statue of Philip the Arab. Musei Capitolini, Roma (Italy).
Philippus Arabs (Musei Capitolini, Rome)

Gordian III, 238?: Philippus Arabs (244-249)? Valerian, 253: Laelianus (268-269)?

Bust of Probus. Musei Capitolini, Roma (Italy). Photo Marco Prins.
Bust of Probus (Musei Capitolini, Rome)

The following units are known from late-ancient sources and are called 'legions'. In fact, they were no longer the elite troops of the Roman empire. The main forces were cavalry units; the legions were the garrisons of the frontier zone.

Aurelian (270-275):

Probus (276-282) Before Diocletian:

Bust of Diocletian. Arkeoloji Müzesi, İstanbul (Turkey). Photo Marco Prins.
Bust of Diocletian (Arkeoloji Müzesi, İstanbul)

Diocletian (284-305):
 


Constantius I Chlorus (293-306):

Bust of Constans. Louvre, Paris (France). Photo Marco Prins.
Constans (Louvre, Paris)

Constantius II (337-361)
Constans (337-350):
 

 
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